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	$36.98	13.161%	$41.8469	$41.85	$41.85	$41.80
Purchase #2	$196.85	10.295%	$217.1157	$217.12	$217.10	$217.10
Purchase #3	$223.73	11.793%	$250.1145	$250.11	$250.10	$250.10
Purchase #4	$103.33	12.859%	$116.6172	$116.62	$116.60	$116.60
Purchase #5	$179.33	5.578%	$189.333	$189.33	$189.35	$189.30
Purchase #6	$29.42	11.873%	$32.913	$32.91	$32.90	$32.90
Purchase #7	$106.63	8.255%	$115.4323	$115.43	$115.45	$115.40
7 purchase totals =	$876.27		$963.3726	$963.37	$963.35	$963.20