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	$188.52	6.381%	$200.5495	$200.55	$200.55	$200.50
Purchase #2	$45.77	6.172%	$48.5949	$48.59	$48.60	$48.60
Purchase #3	$227.69	11.806%	$254.5711	$254.57	$254.55	$254.60
Purchase #4	$35.46	6.768%	$37.8599	$37.86	$37.85	$37.90
Purchase #5	$53.47	11.851%	$59.8067	$59.81	$59.80	$59.80
Purchase #6	$145.69	5.635%	$153.8996	$153.90	$153.90	$153.90
Purchase #7	$31.71	4.187%	$33.0377	$33.04	$33.05	$33.00
7 purchase totals =	$728.31		$788.3194	$788.32	$788.30	$788.30