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	$96.70	4.399%	$100.9538	$100.95	$100.95	$101.00
Purchase #2	$99.89	6.737%	$106.6196	$106.62	$106.60	$106.60
Purchase #3	$54.60	13.235%	$61.8263	$61.83	$61.85	$61.80
Purchase #4	$174.62	12.572%	$196.5732	$196.57	$196.55	$196.60
Purchase #5	$52.25	5.170%	$54.9513	$54.95	$54.95	$55.00
Purchase #6	$161.70	3.480%	$167.3272	$167.33	$167.35	$167.30
Purchase #7	$204.29	11.695%	$228.1817	$228.18	$228.20	$228.20
7 purchase totals =	$844.05		$916.4331	$916.43	$916.45	$916.50