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	$249.57	6.166%	$264.9585	$264.96	$264.95	$265.00
Purchase #2	$80.34	11.760%	$89.788	$89.79	$89.80	$89.80
Purchase #3	$118.37	13.556%	$134.4162	$134.42	$134.40	$134.40
Purchase #4	$71.36	7.833%	$76.9496	$76.95	$76.95	$76.90
Purchase #5	$12.43	11.585%	$13.87	$13.87	$13.85	$13.90
Purchase #6	$108.45	5.422%	$114.3302	$114.33	$114.35	$114.30
Purchase #7	$42.28	10.503%	$46.7207	$46.72	$46.70	$46.70
7 purchase totals =	$682.80		$741.0332	$741.04	$741.00	$741.00