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	$228.43	7.435%	$245.4138	$245.41	$245.40	$245.40
Purchase #2	$59.29	4.195%	$61.7772	$61.78	$61.80	$61.80
Purchase #3	$161.66	10.840%	$179.1839	$179.18	$179.20	$179.20
Purchase #4	$96.30	8.217%	$104.213	$104.21	$104.20	$104.20
Purchase #5	$70.54	11.689%	$78.7854	$78.79	$78.80	$78.80
Purchase #6	$146.26	12.349%	$164.3216	$164.32	$164.30	$164.30
Purchase #7	$29.51	10.173%	$32.5121	$32.51	$32.50	$32.50
7 purchase totals =	$791.99		$866.2070	$866.20	$866.20	$866.20