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	$185.72	13.681%	$211.1284	$211.13	$211.15	$211.10
Purchase #2	$83.47	13.383%	$94.6408	$94.64	$94.65	$94.60
Purchase #3	$239.62	12.269%	$269.019	$269.02	$269.00	$269.00
Purchase #4	$31.33	3.341%	$32.3767	$32.38	$32.40	$32.40
Purchase #5	$147.35	9.209%	$160.9195	$160.92	$160.90	$160.90
Purchase #6	$239.30	5.289%	$251.9566	$251.96	$251.95	$252.00
Purchase #7	$55.72	6.716%	$59.4622	$59.46	$59.45	$59.50
7 purchase totals =	$982.51		$1,079.5032	$1,079.51	$1,079.50	$1,079.50