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	$131.63	13.630%	$149.5712	$149.57	$149.55	$149.60
Purchase #2	$203.71	3.562%	$210.9662	$210.97	$210.95	$211.00
Purchase #3	$165.40	13.315%	$187.423	$187.42	$187.40	$187.40
Purchase #4	$79.89	10.785%	$88.5061	$88.51	$88.50	$88.50
Purchase #5	$62.51	4.197%	$65.1335	$65.13	$65.15	$65.10
Purchase #6	$237.79	5.483%	$250.828	$250.83	$250.85	$250.80
Purchase #7	$84.32	7.476%	$90.6238	$90.62	$90.60	$90.60
7 purchase totals =	$965.25		$1,043.0518	$1,043.05	$1,043.00	$1,043.00