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	$131.61	5.765%	$139.1973	$139.20	$139.20	$139.20
Purchase #2	$200.92	7.805%	$216.6018	$216.60	$216.60	$216.60
Purchase #3	$80.34	11.180%	$89.322	$89.32	$89.30	$89.30
Purchase #4	$158.68	13.662%	$180.3589	$180.36	$180.35	$180.40
Purchase #5	$59.52	8.721%	$64.7107	$64.71	$64.70	$64.70
Purchase #6	$198.87	4.841%	$208.4973	$208.50	$208.50	$208.50
Purchase #7	$183.95	5.127%	$193.3811	$193.38	$193.40	$193.40
7 purchase totals =	$1,013.89		$1,092.0691	$1,092.07	$1,092.05	$1,092.10