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	$118.95	7.199%	$127.5132	$127.51	$127.50	$127.50
Purchase #2	$46.33	11.635%	$51.7205	$51.72	$51.70	$51.70
Purchase #3	$136.83	4.863%	$143.484	$143.48	$143.50	$143.50
Purchase #4	$160.63	12.591%	$180.8549	$180.85	$180.85	$180.90
Purchase #5	$95.96	7.382%	$103.0438	$103.04	$103.05	$103.00
Purchase #6	$28.92	12.874%	$32.6432	$32.64	$32.65	$32.60
Purchase #7	$47.74	12.816%	$53.8584	$53.86	$53.85	$53.90
7 purchase totals =	$635.36		$693.1180	$693.10	$693.10	$693.10