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	$97.53	8.200%	$105.5275	$105.53	$105.55	$105.50
Purchase #2	$118.30	12.401%	$132.9704	$132.97	$132.95	$133.00
Purchase #3	$170.33	7.184%	$182.5665	$182.57	$182.55	$182.60
Purchase #4	$25.66	6.573%	$27.3466	$27.35	$27.35	$27.30
Purchase #5	$231.42	4.411%	$241.6279	$241.63	$241.65	$241.60
Purchase #6	$146.39	4.158%	$152.4769	$152.48	$152.50	$152.50
Purchase #7	$234.51	12.285%	$263.3196	$263.32	$263.30	$263.30
7 purchase totals =	$1,024.14		$1,105.8354	$1,105.85	$1,105.85	$1,105.80