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	$175.61	5.458%	$185.1948	$185.19	$185.20	$185.20
Purchase #2	$26.81	6.404%	$28.5269	$28.53	$28.55	$28.50
Purchase #3	$111.84	5.427%	$117.9096	$117.91	$117.90	$117.90
Purchase #4	$208.86	6.644%	$222.7367	$222.74	$222.75	$222.70
Purchase #5	$79.73	12.480%	$89.6803	$89.68	$89.70	$89.70
Purchase #6	$216.97	7.343%	$232.9021	$232.90	$232.90	$232.90
Purchase #7	$67.45	7.604%	$72.5789	$72.58	$72.60	$72.60
7 purchase totals =	$887.27		$949.5293	$949.53	$949.60	$949.50