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	$109.78	4.698%	$114.9375	$114.94	$114.95	$114.90
Purchase #2	$143.89	6.652%	$153.4616	$153.46	$153.45	$153.50
Purchase #3	$91.25	4.779%	$95.6108	$95.61	$95.60	$95.60
Purchase #4	$250.45	5.109%	$263.2455	$263.25	$263.25	$263.20
Purchase #5	$145.48	9.435%	$159.206	$159.21	$159.20	$159.20
Purchase #6	$124.27	5.682%	$131.331	$131.33	$131.35	$131.30
Purchase #7	$27.53	8.774%	$29.9455	$29.95	$29.95	$29.90
7 purchase totals =	$892.65		$947.7379	$947.75	$947.75	$947.60