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	$169.96	8.293%	$184.0548	$184.05	$184.05	$184.10
Purchase #2	$84.76	4.250%	$88.3623	$88.36	$88.35	$88.40
Purchase #3	$118.50	10.635%	$131.1025	$131.10	$131.10	$131.10
Purchase #4	$142.91	5.750%	$151.1273	$151.13	$151.15	$151.10
Purchase #5	$193.89	3.397%	$200.4764	$200.48	$200.50	$200.50
Purchase #6	$172.69	10.498%	$190.819	$190.82	$190.80	$190.80
Purchase #7	$79.40	9.697%	$87.0994	$87.10	$87.10	$87.10
7 purchase totals =	$962.11		$1,033.0417	$1,033.04	$1,033.05	$1,033.10