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	$57.77	5.465%	$60.9271	$60.93	$60.95	$60.90
Purchase #2	$54.28	13.517%	$61.617	$61.62	$61.60	$61.60
Purchase #3	$38.77	3.456%	$40.1099	$40.11	$40.10	$40.10
Purchase #4	$230.80	4.649%	$241.5299	$241.53	$241.55	$241.50
Purchase #5	$168.34	12.637%	$189.6131	$189.61	$189.60	$189.60
Purchase #6	$132.83	10.456%	$146.7187	$146.72	$146.70	$146.70
Purchase #7	$93.41	4.800%	$97.8937	$97.89	$97.90	$97.90
7 purchase totals =	$776.20		$838.4094	$838.41	$838.40	$838.30