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	$146.76	9.376%	$160.5202	$160.52	$160.50	$160.50
Purchase #2	$151.91	7.266%	$162.9478	$162.95	$162.95	$162.90
Purchase #3	$45.75	10.382%	$50.4998	$50.50	$50.50	$50.50
Purchase #4	$160.45	11.289%	$178.5632	$178.56	$178.55	$178.60
Purchase #5	$182.99	7.280%	$196.3117	$196.31	$196.30	$196.30
Purchase #6	$182.32	6.589%	$194.3331	$194.33	$194.35	$194.30
Purchase #7	$109.82	7.443%	$117.9939	$117.99	$118.00	$118.00
7 purchase totals =	$980.00		$1,061.1697	$1,061.16	$1,061.15	$1,061.10