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	$133.55	3.211%	$137.8383	$137.84	$137.85	$137.80
Purchase #2	$175.59	3.841%	$182.3344	$182.33	$182.35	$182.30
Purchase #3	$49.71	6.810%	$53.0953	$53.10	$53.10	$53.10
Purchase #4	$46.28	8.787%	$50.3466	$50.35	$50.35	$50.30
Purchase #5	$52.30	3.398%	$54.0772	$54.08	$54.10	$54.10
Purchase #6	$24.61	13.183%	$27.8543	$27.85	$27.85	$27.90
Purchase #7	$151.39	4.467%	$158.1526	$158.15	$158.15	$158.20
7 purchase totals =	$633.43		$663.6987	$663.70	$663.75	$663.70