Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$98.66	7.768%	$106.3239	$106.32	$106.30	$106.30
Purchase #2	$224.55	11.585%	$250.5641	$250.56	$250.55	$250.60
Purchase #3	$109.55	7.727%	$118.0149	$118.01	$118.00	$118.00
Purchase #4	$152.57	4.390%	$159.2678	$159.27	$159.25	$159.30
Purchase #5	$146.50	13.527%	$166.3171	$166.32	$166.30	$166.30
Purchase #6	$243.27	13.703%	$276.6053	$276.61	$276.60	$276.60
Purchase #7	$134.62	6.179%	$142.9382	$142.94	$142.95	$142.90
7 purchase totals =	$1,109.72		$1,220.0313	$1,220.03	$1,219.95	$1,220.00