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	$137.71	4.486%	$143.8877	$143.89	$143.90	$143.90
Purchase #2	$55.65	10.523%	$61.506	$61.51	$61.50	$61.50
Purchase #3	$232.72	8.851%	$253.318	$253.32	$253.30	$253.30
Purchase #4	$91.78	12.867%	$103.5893	$103.59	$103.60	$103.60
Purchase #5	$165.36	9.679%	$181.3652	$181.37	$181.35	$181.40
Purchase #6	$118.45	5.697%	$125.1981	$125.20	$125.20	$125.20
Purchase #7	$199.76	6.556%	$212.8563	$212.86	$212.85	$212.90
7 purchase totals =	$1,001.43		$1,081.7206	$1,081.74	$1,081.70	$1,081.80