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	$77.73	10.243%	$85.6919	$85.69	$85.70	$85.70
Purchase #2	$26.57	7.423%	$28.5423	$28.54	$28.55	$28.50
Purchase #3	$111.99	13.640%	$127.2654	$127.27	$127.25	$127.30
Purchase #4	$44.35	11.372%	$49.3935	$49.39	$49.40	$49.40
Purchase #5	$191.34	11.673%	$213.6751	$213.68	$213.70	$213.70
Purchase #6	$151.30	13.133%	$171.1702	$171.17	$171.15	$171.20
Purchase #7	$165.83	9.238%	$181.1494	$181.15	$181.15	$181.10
7 purchase totals =	$769.11		$856.8878	$856.89	$856.90	$856.90