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	$207.65	9.297%	$226.9552	$226.96	$226.95	$227.00
Purchase #2	$88.49	12.310%	$99.3831	$99.38	$99.40	$99.40
Purchase #3	$156.96	7.413%	$168.5954	$168.60	$168.60	$168.60
Purchase #4	$148.93	3.339%	$153.9028	$153.90	$153.90	$153.90
Purchase #5	$88.65	9.502%	$97.0735	$97.07	$97.05	$97.10
Purchase #6	$53.72	9.845%	$59.0087	$59.01	$59.00	$59.00
Purchase #7	$158.64	6.504%	$168.9579	$168.96	$168.95	$169.00
7 purchase totals =	$903.04		$973.8766	$973.88	$973.85	$974.00