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	$45.52	7.279%	$48.8334	$48.83	$48.85	$48.80
Purchase #2	$91.47	10.757%	$101.3094	$101.31	$101.30	$101.30
Purchase #3	$175.78	5.709%	$185.8153	$185.82	$185.80	$185.80
Purchase #4	$121.66	4.271%	$126.8561	$126.86	$126.85	$126.90
Purchase #5	$28.50	4.427%	$29.7617	$29.76	$29.75	$29.80
Purchase #6	$191.39	4.146%	$199.325	$199.33	$199.35	$199.30
Purchase #7	$48.63	6.359%	$51.7224	$51.72	$51.70	$51.70
7 purchase totals =	$702.95		$743.6233	$743.63	$743.60	$743.60