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	$189.74	3.707%	$196.7737	$196.77	$196.75	$196.80
Purchase #2	$144.25	12.497%	$162.2769	$162.28	$162.30	$162.30
Purchase #3	$67.37	6.170%	$71.5267	$71.53	$71.55	$71.50
Purchase #4	$194.73	8.257%	$210.8089	$210.81	$210.80	$210.80
Purchase #5	$12.66	13.280%	$14.3412	$14.34	$14.35	$14.30
Purchase #6	$130.43	8.129%	$141.0327	$141.03	$141.05	$141.00
Purchase #7	$237.53	5.539%	$250.6868	$250.69	$250.70	$250.70
7 purchase totals =	$976.71		$1,047.4469	$1,047.45	$1,047.50	$1,047.40