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	$158.95	8.483%	$172.4337	$172.43	$172.45	$172.40
Purchase #2	$82.53	10.485%	$91.1833	$91.18	$91.20	$91.20
Purchase #3	$78.54	10.313%	$86.6398	$86.64	$86.65	$86.60
Purchase #4	$101.66	11.200%	$113.0459	$113.05	$113.05	$113.00
Purchase #5	$33.89	13.566%	$38.4875	$38.49	$38.50	$38.50
Purchase #6	$229.99	6.756%	$245.5281	$245.53	$245.55	$245.50
Purchase #7	$162.94	10.417%	$179.9135	$179.91	$179.90	$179.90
7 purchase totals =	$848.50		$927.2318	$927.23	$927.30	$927.10