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	$41.60	9.618%	$45.6011	$45.60	$45.60	$45.60
Purchase #2	$57.69	8.432%	$62.5544	$62.55	$62.55	$62.60
Purchase #3	$53.46	7.567%	$57.5053	$57.51	$57.50	$57.50
Purchase #4	$30.72	13.341%	$34.8184	$34.82	$34.80	$34.80
Purchase #5	$18.82	10.382%	$20.7739	$20.77	$20.75	$20.80
Purchase #6	$73.37	9.750%	$80.5236	$80.52	$80.50	$80.50
Purchase #7	$94.45	4.110%	$98.3319	$98.33	$98.35	$98.30
7 purchase totals =	$370.11		$400.1086	$400.10	$400.05	$400.10