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	$30.81	8.529%	$33.4378	$33.44	$33.45	$33.40
Purchase #2	$209.41	4.166%	$218.134	$218.13	$218.15	$218.10
Purchase #3	$131.82	9.415%	$144.2309	$144.23	$144.25	$144.20
Purchase #4	$41.85	12.379%	$47.0306	$47.03	$47.05	$47.00
Purchase #5	$11.68	12.264%	$13.1124	$13.11	$13.10	$13.10
Purchase #6	$54.87	11.560%	$61.213	$61.21	$61.20	$61.20
Purchase #7	$141.29	7.745%	$152.2329	$152.23	$152.25	$152.20
7 purchase totals =	$621.73		$669.3916	$669.38	$669.45	$669.20