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	$175.59	3.405%	$181.5688	$181.57	$181.55	$181.60
Purchase #2	$146.63	8.563%	$159.1859	$159.19	$159.20	$159.20
Purchase #3	$98.79	5.740%	$104.4605	$104.46	$104.45	$104.50
Purchase #4	$89.87	5.273%	$94.6088	$94.61	$94.60	$94.60
Purchase #5	$37.68	3.175%	$38.8763	$38.88	$38.90	$38.90
Purchase #6	$179.48	3.148%	$185.13	$185.13	$185.15	$185.10
Purchase #7	$192.25	11.737%	$214.8144	$214.81	$214.80	$214.80
7 purchase totals =	$920.29		$978.6447	$978.65	$978.65	$978.70