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	$105.97	11.383%	$118.0326	$118.03	$118.05	$118.00
Purchase #2	$150.71	10.449%	$166.4577	$166.46	$166.45	$166.50
Purchase #3	$119.60	8.400%	$129.6464	$129.65	$129.65	$129.60
Purchase #4	$64.33	11.317%	$71.6102	$71.61	$71.60	$71.60
Purchase #5	$236.77	10.855%	$262.4714	$262.47	$262.45	$262.50
Purchase #6	$31.64	6.825%	$33.7994	$33.80	$33.80	$33.80
Purchase #7	$133.72	8.839%	$145.5395	$145.54	$145.55	$145.50
7 purchase totals =	$842.74		$927.5572	$927.56	$927.55	$927.50