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	$49.73	7.742%	$53.5801	$53.58	$53.60	$53.60
Purchase #2	$88.69	13.583%	$100.7368	$100.74	$100.75	$100.70
Purchase #3	$83.74	7.849%	$90.3128	$90.31	$90.30	$90.30
Purchase #4	$78.34	12.112%	$87.8285	$87.83	$87.85	$87.80
Purchase #5	$123.38	6.287%	$131.1369	$131.14	$131.15	$131.10
Purchase #6	$190.60	8.476%	$206.7553	$206.76	$206.75	$206.80
Purchase #7	$85.82	9.485%	$93.96	$93.96	$93.95	$94.00
7 purchase totals =	$700.30		$764.3104	$764.32	$764.35	$764.30