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	$33.36	5.729%	$35.2712	$35.27	$35.25	$35.30
Purchase #2	$244.47	4.550%	$255.5934	$255.59	$255.60	$255.60
Purchase #3	$62.31	11.767%	$69.642	$69.64	$69.65	$69.60
Purchase #4	$138.79	4.351%	$144.8288	$144.83	$144.85	$144.80
Purchase #5	$53.47	12.484%	$60.1452	$60.15	$60.15	$60.10
Purchase #6	$77.28	6.249%	$82.1092	$82.11	$82.10	$82.10
Purchase #7	$63.42	12.165%	$71.135	$71.14	$71.15	$71.10
7 purchase totals =	$673.10		$718.7248	$718.73	$718.75	$718.60