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	$92.79	8.414%	$100.5974	$100.60	$100.60	$100.60
Purchase #2	$57.31	6.184%	$60.8541	$60.85	$60.85	$60.90
Purchase #3	$69.33	4.189%	$72.2342	$72.23	$72.25	$72.20
Purchase #4	$99.35	6.620%	$105.927	$105.93	$105.95	$105.90
Purchase #5	$152.30	8.751%	$165.6278	$165.63	$165.65	$165.60
Purchase #6	$240.91	13.141%	$272.568	$272.57	$272.55	$272.60
Purchase #7	$248.26	9.400%	$271.5964	$271.60	$271.60	$271.60
7 purchase totals =	$960.25		$1,049.4049	$1,049.41	$1,049.45	$1,049.40