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	$150.68	9.587%	$165.1257	$165.13	$165.15	$165.10
Purchase #2	$205.26	10.726%	$227.2762	$227.28	$227.30	$227.30
Purchase #3	$176.28	8.678%	$191.5776	$191.58	$191.60	$191.60
Purchase #4	$204.88	6.663%	$218.5312	$218.53	$218.55	$218.50
Purchase #5	$111.37	10.810%	$123.4091	$123.41	$123.40	$123.40
Purchase #6	$167.47	12.488%	$188.3837	$188.38	$188.40	$188.40
Purchase #7	$83.78	5.236%	$88.1667	$88.17	$88.15	$88.20
7 purchase totals =	$1,099.72		$1,202.4702	$1,202.48	$1,202.55	$1,202.50