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	$67.84	12.822%	$76.5384	$76.54	$76.55	$76.50
Purchase #2	$171.80	8.181%	$185.855	$185.86	$185.85	$185.90
Purchase #3	$99.61	6.287%	$105.8725	$105.87	$105.85	$105.90
Purchase #4	$24.79	6.694%	$26.4494	$26.45	$26.45	$26.40
Purchase #5	$118.48	6.758%	$126.4869	$126.49	$126.50	$126.50
Purchase #6	$120.30	5.694%	$127.1499	$127.15	$127.15	$127.10
Purchase #7	$64.92	13.157%	$73.4615	$73.46	$73.45	$73.50
7 purchase totals =	$667.74		$721.8136	$721.82	$721.80	$721.80