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	$123.91	6.847%	$132.3941	$132.39	$132.40	$132.40
Purchase #2	$64.97	10.539%	$71.8172	$71.82	$71.80	$71.80
Purchase #3	$195.46	8.109%	$211.3099	$211.31	$211.30	$211.30
Purchase #4	$164.28	5.566%	$173.4238	$173.42	$173.40	$173.40
Purchase #5	$67.51	6.834%	$72.1236	$72.12	$72.10	$72.10
Purchase #6	$29.32	5.405%	$30.9047	$30.90	$30.90	$30.90
Purchase #7	$41.42	7.229%	$44.4143	$44.41	$44.40	$44.40
7 purchase totals =	$686.87		$736.3876	$736.37	$736.30	$736.30