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	$20.69	8.492%	$22.447	$22.45	$22.45	$22.40
Purchase #2	$59.58	3.150%	$61.4568	$61.46	$61.45	$61.50
Purchase #3	$79.90	4.557%	$83.541	$83.54	$83.55	$83.50
Purchase #4	$56.77	12.137%	$63.6602	$63.66	$63.65	$63.70
Purchase #5	$134.33	10.749%	$148.7691	$148.77	$148.75	$148.80
Purchase #6	$52.64	4.144%	$54.8214	$54.82	$54.80	$54.80
Purchase #7	$169.99	3.206%	$175.4399	$175.44	$175.45	$175.40
7 purchase totals =	$573.90		$610.1354	$610.14	$610.10	$610.10