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	$33.36	11.756%	$37.2818	$37.28	$37.30	$37.30
Purchase #2	$203.61	3.688%	$211.1191	$211.12	$211.10	$211.10
Purchase #3	$127.59	5.377%	$134.4505	$134.45	$134.45	$134.50
Purchase #4	$90.91	9.136%	$99.2155	$99.22	$99.20	$99.20
Purchase #5	$57.74	8.736%	$62.7842	$62.78	$62.80	$62.80
Purchase #6	$230.54	11.642%	$257.3795	$257.38	$257.40	$257.40
Purchase #7	$22.79	9.327%	$24.9156	$24.92	$24.90	$24.90
7 purchase totals =	$766.54		$827.1462	$827.15	$827.15	$827.20