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	$164.55	13.698%	$187.0901	$187.09	$187.10	$187.10
Purchase #2	$8.55	3.134%	$8.818	$8.82	$8.80	$8.80
Purchase #3	$162.31	4.213%	$169.1481	$169.15	$169.15	$169.10
Purchase #4	$22.85	3.871%	$23.7345	$23.73	$23.75	$23.70
Purchase #5	$23.33	5.199%	$24.5429	$24.54	$24.55	$24.50
Purchase #6	$90.25	4.806%	$94.5874	$94.59	$94.60	$94.60
Purchase #7	$28.51	13.872%	$32.4649	$32.46	$32.45	$32.50
7 purchase totals =	$500.35		$540.3859	$540.38	$540.40	$540.30