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	$60.81	10.442%	$67.1598	$67.16	$67.15	$67.20
Purchase #2	$40.85	11.231%	$45.4379	$45.44	$45.45	$45.40
Purchase #3	$199.30	4.859%	$208.984	$208.98	$209.00	$209.00
Purchase #4	$154.74	3.683%	$160.4391	$160.44	$160.45	$160.40
Purchase #5	$216.64	8.655%	$235.3902	$235.39	$235.40	$235.40
Purchase #6	$56.53	9.354%	$61.8178	$61.82	$61.80	$61.80
Purchase #7	$90.51	5.206%	$95.222	$95.22	$95.20	$95.20
7 purchase totals =	$819.38		$874.4508	$874.45	$874.45	$874.40