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	$97.50	11.169%	$108.3898	$108.39	$108.40	$108.40
Purchase #2	$96.79	4.223%	$100.8774	$100.88	$100.90	$100.90
Purchase #3	$47.46	4.484%	$49.5881	$49.59	$49.60	$49.60
Purchase #4	$67.40	12.830%	$76.0474	$76.05	$76.05	$76.00
Purchase #5	$61.82	4.164%	$64.3942	$64.39	$64.40	$64.40
Purchase #6	$208.47	4.148%	$217.1173	$217.12	$217.10	$217.10
Purchase #7	$31.51	3.287%	$32.5457	$32.55	$32.55	$32.50
7 purchase totals =	$610.95		$648.9599	$648.97	$649.00	$648.90