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	$91.39	3.851%	$94.9094	$94.91	$94.90	$94.90
Purchase #2	$61.69	12.410%	$69.3457	$69.35	$69.35	$69.30
Purchase #3	$117.81	5.199%	$123.9349	$123.93	$123.95	$123.90
Purchase #4	$55.32	10.355%	$61.0484	$61.05	$61.05	$61.00
Purchase #5	$106.97	4.415%	$111.6927	$111.69	$111.70	$111.70
Purchase #6	$146.88	3.809%	$152.4747	$152.47	$152.45	$152.50
Purchase #7	$158.70	12.773%	$178.9708	$178.97	$178.95	$179.00
7 purchase totals =	$738.76		$792.3766	$792.37	$792.35	$792.30