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	$185.42	3.426%	$191.7725	$191.77	$191.75	$191.80
Purchase #2	$89.94	11.500%	$100.2831	$100.28	$100.30	$100.30
Purchase #3	$86.82	8.584%	$94.2726	$94.27	$94.25	$94.30
Purchase #4	$37.75	4.812%	$39.5665	$39.57	$39.55	$39.60
Purchase #5	$214.26	9.608%	$234.8461	$234.85	$234.85	$234.80
Purchase #6	$88.29	11.580%	$98.514	$98.51	$98.50	$98.50
Purchase #7	$202.84	3.693%	$210.3309	$210.33	$210.35	$210.30
7 purchase totals =	$905.32		$969.5857	$969.58	$969.55	$969.60