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	$233.72	9.842%	$256.7227	$256.72	$256.70	$256.70
Purchase #2	$205.39	3.850%	$213.2975	$213.30	$213.30	$213.30
Purchase #3	$59.32	4.168%	$61.7925	$61.79	$61.80	$61.80
Purchase #4	$93.99	4.140%	$97.8812	$97.88	$97.90	$97.90
Purchase #5	$174.29	10.129%	$191.9438	$191.94	$191.95	$191.90
Purchase #6	$18.69	9.401%	$20.447	$20.45	$20.45	$20.40
Purchase #7	$245.67	10.403%	$271.2271	$271.23	$271.25	$271.20
7 purchase totals =	$1,031.07		$1,113.3118	$1,113.31	$1,113.35	$1,113.20