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	$176.38	12.707%	$198.7926	$198.79	$198.80	$198.80
Purchase #2	$241.34	3.130%	$248.8939	$248.89	$248.90	$248.90
Purchase #3	$218.34	11.570%	$243.6019	$243.60	$243.60	$243.60
Purchase #4	$19.56	9.814%	$21.4796	$21.48	$21.50	$21.50
Purchase #5	$239.82	4.420%	$250.42	$250.42	$250.40	$250.40
Purchase #6	$48.82	12.128%	$54.7409	$54.74	$54.75	$54.70
Purchase #7	$100.74	13.443%	$114.2825	$114.28	$114.30	$114.30
7 purchase totals =	$1,045.00		$1,132.2114	$1,132.20	$1,132.25	$1,132.20