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	$197.35	11.632%	$220.3058	$220.31	$220.30	$220.30
Purchase #2	$87.40	4.806%	$91.6004	$91.60	$91.60	$91.60
Purchase #3	$97.37	13.460%	$110.476	$110.48	$110.50	$110.50
Purchase #4	$20.30	3.616%	$21.034	$21.03	$21.05	$21.00
Purchase #5	$196.34	11.106%	$218.1455	$218.15	$218.15	$218.10
Purchase #6	$60.69	3.628%	$62.8918	$62.89	$62.90	$62.90
Purchase #7	$97.86	8.666%	$106.3405	$106.34	$106.35	$106.30
7 purchase totals =	$757.31		$830.7940	$830.80	$830.85	$830.70