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	$115.88	4.810%	$121.4538	$121.45	$121.45	$121.50
Purchase #2	$71.32	8.153%	$77.1347	$77.13	$77.15	$77.10
Purchase #3	$134.98	8.484%	$146.4317	$146.43	$146.45	$146.40
Purchase #4	$160.41	5.804%	$169.7202	$169.72	$169.70	$169.70
Purchase #5	$246.84	9.671%	$270.7119	$270.71	$270.70	$270.70
Purchase #6	$75.82	8.774%	$82.4724	$82.47	$82.45	$82.50
Purchase #7	$247.57	4.851%	$259.5796	$259.58	$259.60	$259.60
7 purchase totals =	$1,052.82		$1,127.5043	$1,127.49	$1,127.50	$1,127.50