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	$38.86	3.844%	$40.3538	$40.35	$40.35	$40.40
Purchase #2	$249.30	6.737%	$266.0953	$266.10	$266.10	$266.10
Purchase #3	$239.64	11.388%	$266.9302	$266.93	$266.95	$266.90
Purchase #4	$54.35	13.874%	$61.8905	$61.89	$61.90	$61.90
Purchase #5	$124.93	11.686%	$139.5293	$139.53	$139.55	$139.50
Purchase #6	$147.47	7.655%	$158.7588	$158.76	$158.75	$158.80
Purchase #7	$151.42	5.262%	$159.3877	$159.39	$159.40	$159.40
7 purchase totals =	$1,005.97		$1,092.9456	$1,092.95	$1,093.00	$1,093.00