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	$140.77	7.292%	$151.0349	$151.03	$151.05	$151.00
Purchase #2	$203.31	9.864%	$223.3645	$223.36	$223.35	$223.40
Purchase #3	$134.96	9.434%	$147.6921	$147.69	$147.70	$147.70
Purchase #4	$68.92	5.177%	$72.488	$72.49	$72.50	$72.50
Purchase #5	$145.36	6.227%	$154.4116	$154.41	$154.40	$154.40
Purchase #6	$66.51	8.735%	$72.3196	$72.32	$72.30	$72.30
Purchase #7	$249.79	8.422%	$270.8273	$270.83	$270.85	$270.80
7 purchase totals =	$1,009.62		$1,092.1380	$1,092.13	$1,092.15	$1,092.10