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	$63.62	6.342%	$67.6548	$67.65	$67.65	$67.70
Purchase #2	$98.44	13.226%	$111.4597	$111.46	$111.45	$111.50
Purchase #3	$91.28	4.142%	$95.0608	$95.06	$95.05	$95.10
Purchase #4	$64.98	10.624%	$71.8835	$71.88	$71.90	$71.90
Purchase #5	$92.36	7.614%	$99.3923	$99.39	$99.40	$99.40
Purchase #6	$232.71	11.700%	$259.9371	$259.94	$259.95	$259.90
Purchase #7	$8.28	10.576%	$9.1557	$9.16	$9.15	$9.20
7 purchase totals =	$651.67		$714.5439	$714.54	$714.55	$714.70