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	$125.54	12.803%	$141.6129	$141.61	$141.60	$141.60
Purchase #2	$61.89	12.750%	$69.781	$69.78	$69.80	$69.80
Purchase #3	$243.71	12.128%	$273.2671	$273.27	$273.25	$273.30
Purchase #4	$118.45	4.275%	$123.5137	$123.51	$123.50	$123.50
Purchase #5	$142.94	7.123%	$153.1216	$153.12	$153.10	$153.10
Purchase #6	$49.44	10.334%	$54.5491	$54.55	$54.55	$54.50
Purchase #7	$123.74	8.192%	$133.8768	$133.88	$133.90	$133.90
7 purchase totals =	$865.71		$949.7222	$949.72	$949.70	$949.70