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	$217.31	12.493%	$244.4585	$244.46	$244.45	$244.50
Purchase #2	$37.78	10.658%	$41.8066	$41.81	$41.80	$41.80
Purchase #3	$105.76	3.798%	$109.7768	$109.78	$109.80	$109.80
Purchase #4	$196.76	12.215%	$220.7942	$220.79	$220.80	$220.80
Purchase #5	$98.37	4.589%	$102.8842	$102.88	$102.90	$102.90
Purchase #6	$33.34	8.473%	$36.1649	$36.16	$36.15	$36.20
Purchase #7	$73.93	4.682%	$77.3914	$77.39	$77.40	$77.40
7 purchase totals =	$763.25		$833.2766	$833.27	$833.30	$833.40