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	$63.94	7.128%	$68.4976	$68.50	$68.50	$68.50
Purchase #2	$103.98	6.803%	$111.0538	$111.05	$111.05	$111.10
Purchase #3	$50.72	7.860%	$54.7066	$54.71	$54.70	$54.70
Purchase #4	$54.98	13.251%	$62.2654	$62.27	$62.25	$62.30
Purchase #5	$39.52	9.425%	$43.2448	$43.24	$43.25	$43.20
Purchase #6	$7.30	8.484%	$7.9193	$7.92	$7.90	$7.90
Purchase #7	$88.76	5.507%	$93.648	$93.65	$93.65	$93.60
7 purchase totals =	$409.20		$441.3355	$441.34	$441.30	$441.30