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	$101.35	10.716%	$112.2107	$112.21	$112.20	$112.20
Purchase #2	$43.27	4.379%	$45.1648	$45.16	$45.15	$45.20
Purchase #3	$213.35	4.222%	$222.3576	$222.36	$222.35	$222.40
Purchase #4	$147.95	4.785%	$155.0294	$155.03	$155.05	$155.00
Purchase #5	$230.65	3.565%	$238.8727	$238.87	$238.85	$238.90
Purchase #6	$7.74	11.507%	$8.6306	$8.63	$8.65	$8.60
Purchase #7	$51.61	5.651%	$54.5265	$54.53	$54.55	$54.50
7 purchase totals =	$795.92		$836.7923	$836.79	$836.80	$836.80