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	$221.25	11.362%	$246.3884	$246.39	$246.40	$246.40
Purchase #2	$141.31	8.113%	$152.7745	$152.77	$152.75	$152.80
Purchase #3	$108.57	3.279%	$112.13	$112.13	$112.15	$112.10
Purchase #4	$47.68	11.291%	$53.0635	$53.06	$53.05	$53.10
Purchase #5	$187.50	6.392%	$199.485	$199.49	$199.50	$199.50
Purchase #6	$133.61	5.568%	$141.0494	$141.05	$141.05	$141.00
Purchase #7	$85.27	4.843%	$89.3996	$89.40	$89.40	$89.40
7 purchase totals =	$925.19		$994.2904	$994.29	$994.30	$994.30