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	$174.52	5.701%	$184.4694	$184.47	$184.45	$184.50
Purchase #2	$105.43	6.129%	$111.8918	$111.89	$111.90	$111.90
Purchase #3	$159.97	3.124%	$164.9675	$164.97	$164.95	$165.00
Purchase #4	$121.65	12.283%	$136.5923	$136.59	$136.60	$136.60
Purchase #5	$45.42	11.654%	$50.7132	$50.71	$50.70	$50.70
Purchase #6	$30.45	11.456%	$33.9384	$33.94	$33.95	$33.90
Purchase #7	$184.39	12.612%	$207.6453	$207.65	$207.65	$207.60
7 purchase totals =	$821.83		$890.2179	$890.22	$890.20	$890.20