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	$189.53	10.867%	$210.1262	$210.13	$210.15	$210.10
Purchase #2	$155.49	8.402%	$168.5543	$168.55	$168.55	$168.60
Purchase #3	$178.94	9.574%	$196.0717	$196.07	$196.05	$196.10
Purchase #4	$150.66	12.623%	$169.6778	$169.68	$169.70	$169.70
Purchase #5	$80.81	12.531%	$90.9363	$90.94	$90.95	$90.90
Purchase #6	$180.39	10.655%	$199.6106	$199.61	$199.60	$199.60
Purchase #7	$128.33	3.343%	$132.6201	$132.62	$132.60	$132.60
7 purchase totals =	$1,064.15		$1,167.5970	$1,167.60	$1,167.60	$1,167.60