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	$136.72	5.711%	$144.5281	$144.53	$144.55	$144.50
Purchase #2	$94.75	11.346%	$105.5003	$105.50	$105.50	$105.50
Purchase #3	$213.25	8.520%	$231.4189	$231.42	$231.40	$231.40
Purchase #4	$5.95	12.142%	$6.6724	$6.67	$6.65	$6.70
Purchase #5	$141.49	8.309%	$153.2464	$153.25	$153.25	$153.20
Purchase #6	$203.65	11.477%	$227.0229	$227.02	$227.00	$227.00
Purchase #7	$100.67	4.361%	$105.0602	$105.06	$105.05	$105.10
7 purchase totals =	$896.48		$973.4492	$973.45	$973.40	$973.40