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	$55.47	8.116%	$59.9719	$59.97	$59.95	$60.00
Purchase #2	$17.76	13.360%	$20.1327	$20.13	$20.15	$20.10
Purchase #3	$110.31	5.729%	$116.6297	$116.63	$116.65	$116.60
Purchase #4	$199.76	11.566%	$222.8642	$222.86	$222.85	$222.90
Purchase #5	$161.42	11.349%	$179.7396	$179.74	$179.75	$179.70
Purchase #6	$208.37	6.115%	$221.1118	$221.11	$221.10	$221.10
Purchase #7	$178.79	11.317%	$199.0237	$199.02	$199.00	$199.00
7 purchase totals =	$931.88		$1,019.4736	$1,019.46	$1,019.45	$1,019.40