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	$105.70	3.177%	$109.0581	$109.06	$109.05	$109.10
Purchase #2	$121.59	7.546%	$130.7652	$130.77	$130.75	$130.80
Purchase #3	$191.65	6.803%	$204.6879	$204.69	$204.70	$204.70
Purchase #4	$179.88	6.110%	$190.8707	$190.87	$190.85	$190.90
Purchase #5	$139.43	5.316%	$146.8421	$146.84	$146.85	$146.80
Purchase #6	$217.75	10.405%	$240.4069	$240.41	$240.40	$240.40
Purchase #7	$65.33	8.516%	$70.8935	$70.89	$70.90	$70.90
7 purchase totals =	$1,021.33		$1,093.5244	$1,093.53	$1,093.50	$1,093.60