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	$57.79	3.747%	$59.9554	$59.96	$59.95	$60.00
Purchase #2	$181.92	4.761%	$190.5812	$190.58	$190.60	$190.60
Purchase #3	$137.66	13.854%	$156.7314	$156.73	$156.75	$156.70
Purchase #4	$89.31	7.617%	$96.1127	$96.11	$96.10	$96.10
Purchase #5	$205.27	9.501%	$224.7727	$224.77	$224.75	$224.80
Purchase #6	$53.77	6.786%	$57.4188	$57.42	$57.40	$57.40
Purchase #7	$152.83	12.640%	$172.1477	$172.15	$172.15	$172.10
7 purchase totals =	$878.55		$957.7199	$957.72	$957.70	$957.70