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	$238.31	6.243%	$253.1877	$253.19	$253.20	$253.20
Purchase #2	$232.54	4.388%	$242.7439	$242.74	$242.75	$242.70
Purchase #3	$171.83	13.812%	$195.5632	$195.56	$195.55	$195.60
Purchase #4	$153.62	11.582%	$171.4123	$171.41	$171.40	$171.40
Purchase #5	$43.92	10.348%	$48.4648	$48.46	$48.45	$48.50
Purchase #6	$57.89	11.180%	$64.3621	$64.36	$64.35	$64.40
Purchase #7	$140.55	5.181%	$147.8319	$147.83	$147.85	$147.80
7 purchase totals =	$1,038.66		$1,123.5659	$1,123.55	$1,123.55	$1,123.60