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	$180.53	5.543%	$190.5368	$190.54	$190.55	$190.50
Purchase #2	$78.43	5.181%	$82.4935	$82.49	$82.50	$82.50
Purchase #3	$246.93	10.549%	$272.9786	$272.98	$273.00	$273.00
Purchase #4	$109.88	6.647%	$117.1837	$117.18	$117.20	$117.20
Purchase #5	$233.35	12.586%	$262.7194	$262.72	$262.70	$262.70
Purchase #6	$231.71	12.111%	$259.7724	$259.77	$259.75	$259.80
Purchase #7	$201.29	7.371%	$216.1271	$216.13	$216.15	$216.10
7 purchase totals =	$1,282.12		$1,401.8115	$1,401.81	$1,401.85	$1,401.80