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	$97.89	8.630%	$106.3379	$106.34	$106.35	$106.30
Purchase #2	$246.41	3.276%	$254.4824	$254.48	$254.50	$254.50
Purchase #3	$203.97	4.484%	$213.116	$213.12	$213.10	$213.10
Purchase #4	$136.58	10.494%	$150.9127	$150.91	$150.90	$150.90
Purchase #5	$112.57	13.412%	$127.6679	$127.67	$127.65	$127.70
Purchase #6	$50.50	13.314%	$57.2236	$57.22	$57.20	$57.20
Purchase #7	$59.55	13.157%	$67.385	$67.39	$67.40	$67.40
7 purchase totals =	$907.47		$977.1255	$977.13	$977.10	$977.10