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	$86.55	3.643%	$89.703	$89.70	$89.70	$89.70
Purchase #2	$40.44	4.636%	$42.3148	$42.31	$42.30	$42.30
Purchase #3	$191.90	6.490%	$204.3543	$204.35	$204.35	$204.40
Purchase #4	$104.85	4.767%	$109.8482	$109.85	$109.85	$109.80
Purchase #5	$154.94	4.278%	$161.5683	$161.57	$161.55	$161.60
Purchase #6	$58.43	3.713%	$60.5995	$60.60	$60.60	$60.60
Purchase #7	$74.61	10.160%	$82.1904	$82.19	$82.20	$82.20
7 purchase totals =	$711.72		$750.5785	$750.57	$750.55	$750.60