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	$182.64	7.776%	$196.8421	$196.84	$196.85	$196.80
Purchase #2	$171.33	13.589%	$194.612	$194.61	$194.60	$194.60
Purchase #3	$151.56	9.470%	$165.9127	$165.91	$165.90	$165.90
Purchase #4	$141.32	11.517%	$157.5958	$157.60	$157.60	$157.60
Purchase #5	$95.63	10.816%	$105.9733	$105.97	$105.95	$106.00
Purchase #6	$80.25	8.299%	$86.9099	$86.91	$86.90	$86.90
Purchase #7	$62.94	8.251%	$68.1332	$68.13	$68.15	$68.10
7 purchase totals =	$885.67		$975.9790	$975.97	$975.95	$975.90