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	$209.29	6.811%	$223.5447	$223.54	$223.55	$223.50
Purchase #2	$180.29	5.713%	$190.59	$190.59	$190.60	$190.60
Purchase #3	$71.98	4.808%	$75.4408	$75.44	$75.45	$75.40
Purchase #4	$225.36	9.719%	$247.2627	$247.26	$247.25	$247.30
Purchase #5	$34.71	6.363%	$36.9186	$36.92	$36.90	$36.90
Purchase #6	$40.38	5.865%	$42.7483	$42.75	$42.75	$42.70
Purchase #7	$188.60	4.285%	$196.6815	$196.68	$196.70	$196.70
7 purchase totals =	$950.61		$1,013.1866	$1,013.18	$1,013.20	$1,013.10