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	$204.41	5.853%	$216.3741	$216.37	$216.35	$216.40
Purchase #2	$130.37	3.111%	$134.4258	$134.43	$134.45	$134.40
Purchase #3	$38.89	7.668%	$41.8721	$41.87	$41.85	$41.90
Purchase #4	$152.82	11.314%	$170.1101	$170.11	$170.10	$170.10
Purchase #5	$50.41	10.276%	$55.5901	$55.59	$55.60	$55.60
Purchase #6	$81.60	12.460%	$91.7674	$91.77	$91.75	$91.80
Purchase #7	$157.80	4.275%	$164.546	$164.55	$164.55	$164.50
7 purchase totals =	$816.30		$874.6856	$874.69	$874.65	$874.70