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	$151.35	11.814%	$169.2305	$169.23	$169.25	$169.20
Purchase #2	$84.72	5.440%	$89.3288	$89.33	$89.35	$89.30
Purchase #3	$26.68	3.551%	$27.6274	$27.63	$27.65	$27.60
Purchase #4	$87.70	3.667%	$90.916	$90.92	$90.90	$90.90
Purchase #5	$81.94	5.521%	$86.4639	$86.46	$86.45	$86.50
Purchase #6	$76.54	12.575%	$86.1649	$86.16	$86.15	$86.20
Purchase #7	$118.93	5.294%	$125.2262	$125.23	$125.25	$125.20
7 purchase totals =	$627.86		$674.9577	$674.96	$675.00	$674.90