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	$34.61	8.546%	$37.5678	$37.57	$37.55	$37.60
Purchase #2	$213.88	5.816%	$226.3193	$226.32	$226.30	$226.30
Purchase #3	$58.83	13.489%	$66.7656	$66.77	$66.75	$66.80
Purchase #4	$10.74	13.112%	$12.1482	$12.15	$12.15	$12.10
Purchase #5	$53.44	3.840%	$55.4921	$55.49	$55.50	$55.50
Purchase #6	$160.50	3.711%	$166.4562	$166.46	$166.45	$166.50
Purchase #7	$160.90	8.490%	$174.5604	$174.56	$174.55	$174.60
7 purchase totals =	$692.90		$739.3096	$739.32	$739.25	$739.40