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	$48.50	9.271%	$52.9964	$53.00	$53.00	$53.00
Purchase #2	$10.79	9.287%	$11.7921	$11.79	$11.80	$11.80
Purchase #3	$39.89	13.732%	$45.3677	$45.37	$45.35	$45.40
Purchase #4	$83.55	7.185%	$89.5531	$89.55	$89.55	$89.60
Purchase #5	$57.54	11.156%	$63.9592	$63.96	$63.95	$64.00
Purchase #6	$235.67	3.225%	$243.2704	$243.27	$243.25	$243.30
Purchase #7	$196.29	7.167%	$210.3581	$210.36	$210.35	$210.40
7 purchase totals =	$672.23		$717.2970	$717.30	$717.25	$717.50