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	$162.59	7.577%	$174.9094	$174.91	$174.90	$174.90
Purchase #2	$200.39	12.443%	$225.3245	$225.32	$225.30	$225.30
Purchase #3	$88.34	13.456%	$100.227	$100.23	$100.25	$100.20
Purchase #4	$207.37	13.869%	$236.1301	$236.13	$236.15	$236.10
Purchase #5	$26.52	4.781%	$27.7879	$27.79	$27.80	$27.80
Purchase #6	$27.70	5.201%	$29.1407	$29.14	$29.15	$29.10
Purchase #7	$232.25	11.441%	$258.8217	$258.82	$258.80	$258.80
7 purchase totals =	$945.16		$1,052.3413	$1,052.34	$1,052.35	$1,052.20