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	$94.33	9.777%	$103.5526	$103.55	$103.55	$103.60
Purchase #2	$130.46	5.378%	$137.4761	$137.48	$137.50	$137.50
Purchase #3	$195.32	12.198%	$219.1451	$219.15	$219.15	$219.10
Purchase #4	$137.69	4.562%	$143.9714	$143.97	$143.95	$144.00
Purchase #5	$5.57	4.430%	$5.8168	$5.82	$5.80	$5.80
Purchase #6	$185.60	4.821%	$194.5478	$194.55	$194.55	$194.50
Purchase #7	$189.79	4.274%	$197.9016	$197.90	$197.90	$197.90
7 purchase totals =	$938.76		$1,002.4114	$1,002.42	$1,002.40	$1,002.40