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	$211.39	5.133%	$222.2406	$222.24	$222.25	$222.20
Purchase #2	$66.49	9.592%	$72.8677	$72.87	$72.85	$72.90
Purchase #3	$170.67	10.503%	$188.5955	$188.60	$188.60	$188.60
Purchase #4	$231.64	10.640%	$256.2865	$256.29	$256.30	$256.30
Purchase #5	$210.96	8.218%	$228.2967	$228.30	$228.30	$228.30
Purchase #6	$155.41	10.234%	$171.3147	$171.31	$171.30	$171.30
Purchase #7	$114.51	3.769%	$118.8259	$118.83	$118.85	$118.80
7 purchase totals =	$1,161.07		$1,258.4276	$1,258.44	$1,258.45	$1,258.40