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	$188.61	12.465%	$212.1202	$212.12	$212.10	$212.10
Purchase #2	$6.59	3.118%	$6.7955	$6.80	$6.80	$6.80
Purchase #3	$108.89	13.239%	$123.3059	$123.31	$123.30	$123.30
Purchase #4	$49.63	6.248%	$52.7309	$52.73	$52.75	$52.70
Purchase #5	$162.39	8.316%	$175.8944	$175.89	$175.90	$175.90
Purchase #6	$34.68	11.300%	$38.5988	$38.60	$38.60	$38.60
Purchase #7	$160.54	5.500%	$169.3697	$169.37	$169.35	$169.40
7 purchase totals =	$711.33		$778.8154	$778.82	$778.80	$778.80