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	$140.65	8.741%	$152.9442	$152.94	$152.95	$152.90
Purchase #2	$223.78	11.504%	$249.5237	$249.52	$249.50	$249.50
Purchase #3	$143.80	8.839%	$156.5105	$156.51	$156.50	$156.50
Purchase #4	$55.38	10.318%	$61.0941	$61.09	$61.10	$61.10
Purchase #5	$86.38	3.772%	$89.6383	$89.64	$89.65	$89.60
Purchase #6	$94.36	4.814%	$98.9025	$98.90	$98.90	$98.90
Purchase #7	$224.28	6.485%	$238.8246	$238.82	$238.80	$238.80
7 purchase totals =	$968.63		$1,047.4379	$1,047.42	$1,047.40	$1,047.30