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	$114.71	13.675%	$130.3966	$130.40	$130.40	$130.40
Purchase #2	$228.47	6.756%	$243.9054	$243.91	$243.90	$243.90
Purchase #3	$67.32	7.495%	$72.3656	$72.37	$72.35	$72.40
Purchase #4	$166.40	13.335%	$188.5894	$188.59	$188.60	$188.60
Purchase #5	$38.30	8.352%	$41.4988	$41.50	$41.50	$41.50
Purchase #6	$132.48	11.304%	$147.4555	$147.46	$147.45	$147.50
Purchase #7	$69.45	8.522%	$75.3685	$75.37	$75.35	$75.40
7 purchase totals =	$817.13		$899.5798	$899.60	$899.55	$899.70