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	$98.98	12.449%	$111.302	$111.30	$111.30	$111.30
Purchase #2	$158.90	4.523%	$166.087	$166.09	$166.10	$166.10
Purchase #3	$49.67	6.329%	$52.8136	$52.81	$52.80	$52.80
Purchase #4	$135.74	12.194%	$152.2921	$152.29	$152.30	$152.30
Purchase #5	$152.96	10.805%	$169.4873	$169.49	$169.50	$169.50
Purchase #6	$98.54	11.515%	$109.8869	$109.89	$109.90	$109.90
Purchase #7	$195.70	12.739%	$220.6302	$220.63	$220.65	$220.60
7 purchase totals =	$890.49		$982.4991	$982.50	$982.55	$982.50