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	$146.29	4.465%	$152.8218	$152.82	$152.80	$152.80
Purchase #2	$237.60	11.268%	$264.3728	$264.37	$264.35	$264.40
Purchase #3	$244.44	13.754%	$278.0603	$278.06	$278.05	$278.10
Purchase #4	$181.77	8.272%	$196.806	$196.81	$196.80	$196.80
Purchase #5	$141.70	6.473%	$150.8722	$150.87	$150.85	$150.90
Purchase #6	$189.48	5.454%	$199.8142	$199.81	$199.80	$199.80
Purchase #7	$112.35	13.243%	$127.2285	$127.23	$127.25	$127.20
7 purchase totals =	$1,253.63		$1,369.9758	$1,369.97	$1,369.90	$1,370.00