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	$237.77	11.518%	$265.1563	$265.16	$265.15	$265.20
Purchase #2	$77.41	11.256%	$86.1233	$86.12	$86.10	$86.10
Purchase #3	$89.58	4.151%	$93.2985	$93.30	$93.30	$93.30
Purchase #4	$96.85	11.667%	$108.1495	$108.15	$108.15	$108.10
Purchase #5	$92.43	5.211%	$97.2465	$97.25	$97.25	$97.20
Purchase #6	$69.66	11.523%	$77.6869	$77.69	$77.70	$77.70
Purchase #7	$43.86	4.538%	$45.8504	$45.85	$45.85	$45.90
7 purchase totals =	$707.56		$773.5114	$773.52	$773.50	$773.50