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	$216.51	4.195%	$225.5926	$225.59	$225.60	$225.60
Purchase #2	$126.86	8.679%	$137.8702	$137.87	$137.85	$137.90
Purchase #3	$197.32	6.692%	$210.5247	$210.52	$210.50	$210.50
Purchase #4	$16.71	6.810%	$17.848	$17.85	$17.85	$17.80
Purchase #5	$183.63	8.653%	$199.5195	$199.52	$199.50	$199.50
Purchase #6	$228.42	7.562%	$245.6931	$245.69	$245.70	$245.70
Purchase #7	$167.88	10.220%	$185.0373	$185.04	$185.05	$185.00
7 purchase totals =	$1,137.33		$1,222.0854	$1,222.08	$1,222.05	$1,222.00