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	$244.85	9.819%	$268.8918	$268.89	$268.90	$268.90
Purchase #2	$73.65	6.112%	$78.1515	$78.15	$78.15	$78.20
Purchase #3	$152.77	3.785%	$158.5523	$158.55	$158.55	$158.60
Purchase #4	$69.35	3.240%	$71.5969	$71.60	$71.60	$71.60
Purchase #5	$79.46	11.228%	$88.3818	$88.38	$88.40	$88.40
Purchase #6	$132.32	6.584%	$141.0319	$141.03	$141.05	$141.00
Purchase #7	$146.27	10.489%	$161.6123	$161.61	$161.60	$161.60
7 purchase totals =	$898.67		$968.2185	$968.21	$968.25	$968.30