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	$104.63	6.764%	$111.7072	$111.71	$111.70	$111.70
Purchase #2	$170.35	6.857%	$182.0309	$182.03	$182.05	$182.00
Purchase #3	$33.35	13.432%	$37.8296	$37.83	$37.85	$37.80
Purchase #4	$195.81	7.437%	$210.3724	$210.37	$210.35	$210.40
Purchase #5	$172.41	12.701%	$194.3078	$194.31	$194.30	$194.30
Purchase #6	$241.70	11.477%	$269.4399	$269.44	$269.45	$269.40
Purchase #7	$151.41	5.578%	$159.8556	$159.86	$159.85	$159.90
7 purchase totals =	$1,069.66		$1,165.5434	$1,165.55	$1,165.55	$1,165.50