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	$188.42	5.634%	$199.0356	$199.04	$199.05	$199.00
Purchase #2	$175.64	5.627%	$185.5233	$185.52	$185.50	$185.50
Purchase #3	$93.64	7.711%	$100.8606	$100.86	$100.85	$100.90
Purchase #4	$70.96	4.837%	$74.3923	$74.39	$74.40	$74.40
Purchase #5	$111.48	3.223%	$115.073	$115.07	$115.05	$115.10
Purchase #6	$51.50	4.250%	$53.6888	$53.69	$53.70	$53.70
Purchase #7	$121.28	5.799%	$128.313	$128.31	$128.30	$128.30
7 purchase totals =	$812.92		$856.8866	$856.88	$856.85	$856.90