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	$153.29	8.520%	$166.3503	$166.35	$166.35	$166.40
Purchase #2	$71.47	3.443%	$73.9307	$73.93	$73.95	$73.90
Purchase #3	$39.74	10.405%	$43.8749	$43.87	$43.85	$43.90
Purchase #4	$49.52	10.764%	$54.8503	$54.85	$54.85	$54.90
Purchase #5	$225.35	12.823%	$254.2466	$254.25	$254.25	$254.20
Purchase #6	$167.59	6.325%	$178.1901	$178.19	$178.20	$178.20
Purchase #7	$60.94	5.504%	$64.2941	$64.29	$64.30	$64.30
7 purchase totals =	$767.90		$835.7370	$835.73	$835.75	$835.80