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	$233.53	8.737%	$253.9335	$253.93	$253.95	$253.90
Purchase #2	$115.47	7.440%	$124.061	$124.06	$124.05	$124.10
Purchase #3	$83.47	8.700%	$90.7319	$90.73	$90.75	$90.70
Purchase #4	$140.64	7.337%	$150.9588	$150.96	$150.95	$151.00
Purchase #5	$137.59	4.856%	$144.2714	$144.27	$144.25	$144.30
Purchase #6	$48.50	12.711%	$54.6648	$54.66	$54.65	$54.70
Purchase #7	$66.50	12.166%	$74.5904	$74.59	$74.60	$74.60
7 purchase totals =	$825.70		$893.2118	$893.20	$893.20	$893.30