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	$187.59	12.335%	$210.7292	$210.73	$210.75	$210.70
Purchase #2	$81.38	9.586%	$89.1811	$89.18	$89.20	$89.20
Purchase #3	$83.90	12.227%	$94.1585	$94.16	$94.15	$94.20
Purchase #4	$233.71	4.618%	$244.5027	$244.50	$244.50	$244.50
Purchase #5	$90.83	10.736%	$100.5815	$100.58	$100.60	$100.60
Purchase #6	$141.46	8.843%	$153.9693	$153.97	$153.95	$154.00
Purchase #7	$7.39	13.635%	$8.3976	$8.40	$8.40	$8.40
7 purchase totals =	$826.26		$901.5199	$901.52	$901.55	$901.60