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	$160.85	11.806%	$179.84	$179.84	$179.85	$179.80
Purchase #2	$138.91	12.654%	$156.4877	$156.49	$156.50	$156.50
Purchase #3	$228.45	6.506%	$243.313	$243.31	$243.30	$243.30
Purchase #4	$92.84	10.696%	$102.7702	$102.77	$102.75	$102.80
Purchase #5	$209.65	8.161%	$226.7595	$226.76	$226.75	$226.80
Purchase #6	$227.37	3.326%	$234.9323	$234.93	$234.95	$234.90
Purchase #7	$97.93	13.627%	$111.2749	$111.27	$111.25	$111.30
7 purchase totals =	$1,156.00		$1,255.3776	$1,255.37	$1,255.35	$1,255.40