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	$80.53	10.309%	$88.8318	$88.83	$88.85	$88.80
Purchase #2	$62.73	9.764%	$68.855	$68.86	$68.85	$68.90
Purchase #3	$78.60	9.258%	$85.8768	$85.88	$85.90	$85.90
Purchase #4	$107.62	3.496%	$111.3824	$111.38	$111.40	$111.40
Purchase #5	$205.94	3.343%	$212.8246	$212.82	$212.80	$212.80
Purchase #6	$230.45	7.517%	$247.7729	$247.77	$247.75	$247.80
Purchase #7	$133.46	5.619%	$140.9591	$140.96	$140.95	$141.00
7 purchase totals =	$899.33		$956.5026	$956.50	$956.50	$956.60