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	$209.41	6.275%	$222.5505	$222.55	$222.55	$222.60
Purchase #2	$239.86	13.810%	$272.9847	$272.98	$273.00	$273.00
Purchase #3	$84.60	7.145%	$90.6447	$90.64	$90.65	$90.60
Purchase #4	$154.82	11.530%	$172.6707	$172.67	$172.65	$172.70
Purchase #5	$49.58	6.656%	$52.88	$52.88	$52.90	$52.90
Purchase #6	$57.27	9.529%	$62.7273	$62.73	$62.75	$62.70
Purchase #7	$170.74	6.742%	$182.2513	$182.25	$182.25	$182.30
7 purchase totals =	$966.28		$1,056.7092	$1,056.70	$1,056.75	$1,056.80