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	$176.65	5.174%	$185.7899	$185.79	$185.80	$185.80
Purchase #2	$59.54	10.178%	$65.6	$65.60	$65.60	$65.60
Purchase #3	$21.59	4.546%	$22.5715	$22.57	$22.55	$22.60
Purchase #4	$113.54	10.677%	$125.6627	$125.66	$125.65	$125.70
Purchase #5	$37.64	13.187%	$42.6036	$42.60	$42.60	$42.60
Purchase #6	$101.81	7.764%	$109.7145	$109.71	$109.70	$109.70
Purchase #7	$244.83	4.663%	$256.2464	$256.25	$256.25	$256.20
7 purchase totals =	$755.60		$808.1886	$808.18	$808.15	$808.20