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	$133.59	4.727%	$139.9048	$139.90	$139.90	$139.90
Purchase #2	$103.47	3.181%	$106.7614	$106.76	$106.75	$106.80
Purchase #3	$29.75	7.832%	$32.08	$32.08	$32.10	$32.10
Purchase #4	$178.86	9.666%	$196.1486	$196.15	$196.15	$196.10
Purchase #5	$41.52	9.386%	$45.4171	$45.42	$45.40	$45.40
Purchase #6	$29.86	7.317%	$32.0449	$32.04	$32.05	$32.00
Purchase #7	$178.45	3.792%	$185.2168	$185.22	$185.20	$185.20
7 purchase totals =	$695.50		$737.5736	$737.57	$737.55	$737.50