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	$107.98	4.737%	$113.095	$113.10	$113.10	$113.10
Purchase #2	$246.41	6.299%	$261.9314	$261.93	$261.95	$261.90
Purchase #3	$141.56	6.164%	$150.2858	$150.29	$150.30	$150.30
Purchase #4	$32.33	10.793%	$35.8194	$35.82	$35.80	$35.80
Purchase #5	$46.44	5.102%	$48.8094	$48.81	$48.80	$48.80
Purchase #6	$138.31	5.824%	$146.3652	$146.37	$146.35	$146.40
Purchase #7	$56.89	13.512%	$64.577	$64.58	$64.60	$64.60
7 purchase totals =	$769.92		$820.8832	$820.90	$820.90	$820.90