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	$185.67	13.817%	$211.324	$211.32	$211.30	$211.30
Purchase #2	$207.81	7.655%	$223.7179	$223.72	$223.70	$223.70
Purchase #3	$71.39	4.401%	$74.5319	$74.53	$74.55	$74.50
Purchase #4	$176.30	5.185%	$185.4412	$185.44	$185.45	$185.40
Purchase #5	$171.59	13.664%	$195.0361	$195.04	$195.05	$195.00
Purchase #6	$225.50	10.807%	$249.8698	$249.87	$249.85	$249.90
Purchase #7	$250.42	12.827%	$282.5414	$282.54	$282.55	$282.50
7 purchase totals =	$1,288.68		$1,422.4623	$1,422.46	$1,422.45	$1,422.30