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	$53.69	10.632%	$59.3983	$59.40	$59.40	$59.40
Purchase #2	$48.46	13.460%	$54.9827	$54.98	$55.00	$55.00
Purchase #3	$195.67	5.107%	$205.6629	$205.66	$205.65	$205.70
Purchase #4	$144.98	9.151%	$158.2471	$158.25	$158.25	$158.20
Purchase #5	$23.88	3.653%	$24.7523	$24.75	$24.75	$24.80
Purchase #6	$40.37	4.747%	$42.2864	$42.29	$42.30	$42.30
Purchase #7	$125.60	3.832%	$130.413	$130.41	$130.40	$130.40
7 purchase totals =	$632.65		$675.7427	$675.74	$675.75	$675.80