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	$111.34	12.248%	$124.9769	$124.98	$125.00	$125.00
Purchase #2	$203.76	6.303%	$216.603	$216.60	$216.60	$216.60
Purchase #3	$132.74	11.399%	$147.871	$147.87	$147.85	$147.90
Purchase #4	$101.48	3.447%	$104.978	$104.98	$105.00	$105.00
Purchase #5	$99.61	11.865%	$111.4287	$111.43	$111.45	$111.40
Purchase #6	$77.39	4.296%	$80.7147	$80.71	$80.70	$80.70
Purchase #7	$117.48	3.456%	$121.5401	$121.54	$121.55	$121.50
7 purchase totals =	$843.80		$908.1124	$908.11	$908.15	$908.10