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	$31.91	3.816%	$33.1277	$33.13	$33.15	$33.10
Purchase #2	$87.51	7.476%	$94.0522	$94.05	$94.05	$94.10
Purchase #3	$178.80	4.558%	$186.9497	$186.95	$186.95	$186.90
Purchase #4	$220.51	9.788%	$242.0935	$242.09	$242.10	$242.10
Purchase #5	$178.53	3.785%	$185.2874	$185.29	$185.30	$185.30
Purchase #6	$208.86	6.847%	$223.1606	$223.16	$223.15	$223.20
Purchase #7	$250.27	5.649%	$264.4078	$264.41	$264.40	$264.40
7 purchase totals =	$1,156.39		$1,229.0789	$1,229.08	$1,229.10	$1,229.10