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	$96.98	11.416%	$108.0512	$108.05	$108.05	$108.10
Purchase #2	$53.93	7.368%	$57.9036	$57.90	$57.90	$57.90
Purchase #3	$57.89	10.839%	$64.1647	$64.16	$64.15	$64.20
Purchase #4	$198.47	9.162%	$216.6538	$216.65	$216.65	$216.70
Purchase #5	$96.85	9.214%	$105.7738	$105.77	$105.75	$105.80
Purchase #6	$229.77	11.267%	$255.6582	$255.66	$255.65	$255.70
Purchase #7	$159.57	5.556%	$168.4357	$168.44	$168.45	$168.40
7 purchase totals =	$893.46		$976.6410	$976.63	$976.60	$976.80