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	$84.51	7.597%	$90.9302	$90.93	$90.95	$90.90
Purchase #2	$92.61	11.586%	$103.3398	$103.34	$103.35	$103.30
Purchase #3	$230.49	3.525%	$238.6148	$238.61	$238.60	$238.60
Purchase #4	$60.77	8.732%	$66.0764	$66.08	$66.10	$66.10
Purchase #5	$87.73	12.323%	$98.541	$98.54	$98.55	$98.50
Purchase #6	$99.90	8.549%	$108.4405	$108.44	$108.45	$108.40
Purchase #7	$115.41	4.330%	$120.4073	$120.41	$120.40	$120.40
7 purchase totals =	$771.42		$826.3500	$826.35	$826.40	$826.20