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	$20.97	6.274%	$22.2857	$22.29	$22.30	$22.30
Purchase #2	$172.49	4.224%	$179.776	$179.78	$179.80	$179.80
Purchase #3	$184.39	4.533%	$192.7484	$192.75	$192.75	$192.70
Purchase #4	$152.37	13.425%	$172.8257	$172.83	$172.85	$172.80
Purchase #5	$58.73	12.104%	$65.8387	$65.84	$65.85	$65.80
Purchase #6	$139.48	10.618%	$154.29	$154.29	$154.30	$154.30
Purchase #7	$239.60	8.467%	$259.8869	$259.89	$259.90	$259.90
7 purchase totals =	$968.03		$1,047.6514	$1,047.67	$1,047.75	$1,047.60