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	$63.55	7.477%	$68.3016	$68.30	$68.30	$68.30
Purchase #2	$152.69	11.715%	$170.5776	$170.58	$170.60	$170.60
Purchase #3	$66.51	7.705%	$71.6346	$71.63	$71.65	$71.60
Purchase #4	$187.59	12.492%	$211.0237	$211.02	$211.00	$211.00
Purchase #5	$239.34	11.806%	$267.5965	$267.60	$267.60	$267.60
Purchase #6	$153.88	11.472%	$171.5331	$171.53	$171.55	$171.50
Purchase #7	$66.91	7.433%	$71.8834	$71.88	$71.90	$71.90
7 purchase totals =	$930.47		$1,032.5505	$1,032.54	$1,032.60	$1,032.50