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	$72.73	13.239%	$82.3587	$82.36	$82.35	$82.40
Purchase #2	$105.25	3.429%	$108.859	$108.86	$108.85	$108.90
Purchase #3	$101.82	13.251%	$115.3122	$115.31	$115.30	$115.30
Purchase #4	$157.76	5.311%	$166.1386	$166.14	$166.15	$166.10
Purchase #5	$113.25	10.192%	$124.7924	$124.79	$124.80	$124.80
Purchase #6	$248.91	10.624%	$275.3542	$275.35	$275.35	$275.40
Purchase #7	$119.97	8.430%	$130.0835	$130.08	$130.10	$130.10
7 purchase totals =	$919.69		$1,002.8986	$1,002.89	$1,002.90	$1,003.00