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	$223.76	4.153%	$233.0528	$233.05	$233.05	$233.10
Purchase #2	$86.51	8.814%	$94.135	$94.14	$94.15	$94.10
Purchase #3	$26.25	13.462%	$29.7838	$29.78	$29.80	$29.80
Purchase #4	$82.52	3.399%	$85.3249	$85.32	$85.30	$85.30
Purchase #5	$187.93	13.476%	$213.2554	$213.26	$213.25	$213.30
Purchase #6	$172.96	9.569%	$189.5105	$189.51	$189.50	$189.50
Purchase #7	$205.38	12.749%	$231.5639	$231.56	$231.55	$231.60
7 purchase totals =	$985.31		$1,076.6263	$1,076.62	$1,076.60	$1,076.70