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	$96.45	3.387%	$99.7168	$99.72	$99.70	$99.70
Purchase #2	$100.95	3.864%	$104.8507	$104.85	$104.85	$104.90
Purchase #3	$101.74	3.488%	$105.2887	$105.29	$105.30	$105.30
Purchase #4	$245.37	11.699%	$274.0758	$274.08	$274.10	$274.10
Purchase #5	$161.28	3.581%	$167.0554	$167.06	$167.05	$167.10
Purchase #6	$107.39	12.630%	$120.9534	$120.95	$120.95	$121.00
Purchase #7	$154.78	13.260%	$175.3038	$175.30	$175.30	$175.30
7 purchase totals =	$967.96		$1,047.2446	$1,047.25	$1,047.25	$1,047.40