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	$121.32	7.452%	$130.3608	$130.36	$130.35	$130.40
Purchase #2	$158.78	13.655%	$180.4614	$180.46	$180.45	$180.50
Purchase #3	$155.53	6.362%	$165.4248	$165.42	$165.40	$165.40
Purchase #4	$155.64	12.173%	$174.5861	$174.59	$174.60	$174.60
Purchase #5	$10.93	7.816%	$11.7843	$11.78	$11.80	$11.80
Purchase #6	$182.78	7.337%	$196.1906	$196.19	$196.20	$196.20
Purchase #7	$94.59	3.656%	$98.0482	$98.05	$98.05	$98.00
7 purchase totals =	$879.57		$956.8562	$956.85	$956.85	$956.90