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	$221.90	9.237%	$242.3969	$242.40	$242.40	$242.40
Purchase #2	$64.37	13.264%	$72.908	$72.91	$72.90	$72.90
Purchase #3	$130.32	12.211%	$146.2334	$146.23	$146.25	$146.20
Purchase #4	$174.48	12.736%	$196.7018	$196.70	$196.70	$196.70
Purchase #5	$182.40	13.262%	$206.5899	$206.59	$206.60	$206.60
Purchase #6	$231.95	3.429%	$239.9036	$239.90	$239.90	$239.90
Purchase #7	$35.78	13.519%	$40.6171	$40.62	$40.60	$40.60
7 purchase totals =	$1,041.20		$1,145.3507	$1,145.35	$1,145.35	$1,145.30