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	$227.45	10.464%	$251.2504	$251.25	$251.25	$251.30
Purchase #2	$226.97	12.680%	$255.7498	$255.75	$255.75	$255.70
Purchase #3	$95.30	6.566%	$101.5574	$101.56	$101.55	$101.60
Purchase #4	$89.43	12.297%	$100.4272	$100.43	$100.45	$100.40
Purchase #5	$12.75	7.672%	$13.7282	$13.73	$13.75	$13.70
Purchase #6	$243.50	7.677%	$262.1935	$262.19	$262.20	$262.20
Purchase #7	$141.30	13.465%	$160.326	$160.33	$160.35	$160.30
7 purchase totals =	$1,036.70		$1,145.2325	$1,145.24	$1,145.30	$1,145.20