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	$49.41	8.718%	$53.7176	$53.72	$53.70	$53.70
Purchase #2	$66.65	7.328%	$71.5341	$71.53	$71.55	$71.50
Purchase #3	$139.33	10.269%	$153.6378	$153.64	$153.65	$153.60
Purchase #4	$200.80	9.173%	$219.2194	$219.22	$219.20	$219.20
Purchase #5	$71.96	8.677%	$78.204	$78.20	$78.20	$78.20
Purchase #6	$189.56	8.740%	$206.1275	$206.13	$206.15	$206.10
Purchase #7	$41.70	4.185%	$43.4451	$43.45	$43.45	$43.40
7 purchase totals =	$759.41		$825.8855	$825.89	$825.90	$825.70