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	$43.87	4.414%	$45.8064	$45.81	$45.80	$45.80
Purchase #2	$70.88	3.329%	$73.2396	$73.24	$73.25	$73.20
Purchase #3	$199.63	11.729%	$223.0446	$223.04	$223.05	$223.00
Purchase #4	$54.84	11.280%	$61.026	$61.03	$61.05	$61.00
Purchase #5	$243.25	5.560%	$256.7747	$256.77	$256.75	$256.80
Purchase #6	$134.33	6.799%	$143.4631	$143.46	$143.45	$143.50
Purchase #7	$61.96	5.679%	$65.4787	$65.48	$65.50	$65.50
7 purchase totals =	$808.76		$868.8331	$868.83	$868.85	$868.80