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	$226.56	9.626%	$248.3687	$248.37	$248.35	$248.40
Purchase #2	$57.61	6.493%	$61.3506	$61.35	$61.35	$61.40
Purchase #3	$80.29	8.226%	$86.8947	$86.89	$86.90	$86.90
Purchase #4	$95.46	3.322%	$98.6312	$98.63	$98.65	$98.60
Purchase #5	$221.61	9.370%	$242.3749	$242.37	$242.35	$242.40
Purchase #6	$29.50	6.468%	$31.4081	$31.41	$31.40	$31.40
Purchase #7	$178.29	11.524%	$198.8361	$198.84	$198.85	$198.80
7 purchase totals =	$889.32		$967.8643	$967.86	$967.85	$967.90