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	$248.92	9.856%	$273.4536	$273.45	$273.45	$273.50
Purchase #2	$80.47	8.427%	$87.2512	$87.25	$87.25	$87.30
Purchase #3	$32.73	8.385%	$35.4744	$35.47	$35.45	$35.50
Purchase #4	$83.64	3.689%	$86.7255	$86.73	$86.75	$86.70
Purchase #5	$247.61	13.751%	$281.6589	$281.66	$281.65	$281.70
Purchase #6	$142.86	12.375%	$160.5389	$160.54	$160.55	$160.50
Purchase #7	$69.27	3.557%	$71.7339	$71.73	$71.75	$71.70
7 purchase totals =	$905.50		$996.8364	$996.83	$996.85	$996.90