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	$62.86	12.814%	$70.9149	$70.91	$70.90	$70.90
Purchase #2	$245.39	6.542%	$261.4434	$261.44	$261.45	$261.40
Purchase #3	$32.75	13.676%	$37.2289	$37.23	$37.25	$37.20
Purchase #4	$59.34	5.454%	$62.5764	$62.58	$62.60	$62.60
Purchase #5	$93.55	6.653%	$99.7739	$99.77	$99.75	$99.80
Purchase #6	$60.50	6.224%	$64.2655	$64.27	$64.25	$64.30
Purchase #7	$195.85	7.256%	$210.0609	$210.06	$210.05	$210.10
7 purchase totals =	$750.24		$806.2639	$806.26	$806.25	$806.30