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	$61.55	6.450%	$65.52	$65.52	$65.50	$65.50
Purchase #2	$218.64	7.250%	$234.4914	$234.49	$234.50	$234.50
Purchase #3	$19.32	8.794%	$21.019	$21.02	$21.00	$21.00
Purchase #4	$76.40	5.113%	$80.3063	$80.31	$80.30	$80.30
Purchase #5	$151.47	8.526%	$164.3843	$164.38	$164.40	$164.40
Purchase #6	$37.66	5.851%	$39.8635	$39.86	$39.85	$39.90
Purchase #7	$107.50	11.850%	$120.2388	$120.24	$120.25	$120.20
7 purchase totals =	$672.54		$725.8233	$725.82	$725.80	$725.80