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	$100.90	10.563%	$111.5581	$111.56	$111.55	$111.60
Purchase #2	$42.95	7.133%	$46.0136	$46.01	$46.00	$46.00
Purchase #3	$148.45	13.863%	$169.0296	$169.03	$169.05	$169.00
Purchase #4	$54.90	3.384%	$56.7578	$56.76	$56.75	$56.80
Purchase #5	$72.90	5.809%	$77.1348	$77.13	$77.15	$77.10
Purchase #6	$63.62	13.714%	$72.3448	$72.34	$72.35	$72.30
Purchase #7	$169.67	8.625%	$184.304	$184.30	$184.30	$184.30
7 purchase totals =	$653.39		$717.1427	$717.13	$717.15	$717.10