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	$241.80	10.553%	$267.3172	$267.32	$267.30	$267.30
Purchase #2	$41.67	8.606%	$45.2561	$45.26	$45.25	$45.30
Purchase #3	$197.98	10.649%	$219.0629	$219.06	$219.05	$219.10
Purchase #4	$53.60	10.470%	$59.2119	$59.21	$59.20	$59.20
Purchase #5	$106.89	11.804%	$119.5073	$119.51	$119.50	$119.50
Purchase #6	$96.60	9.431%	$105.7103	$105.71	$105.70	$105.70
Purchase #7	$248.85	6.273%	$264.4604	$264.46	$264.45	$264.50
7 purchase totals =	$987.39		$1,080.5261	$1,080.53	$1,080.45	$1,080.60