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	$117.35	12.515%	$132.0364	$132.04	$132.05	$132.00
Purchase #2	$99.85	4.130%	$103.9738	$103.97	$103.95	$104.00
Purchase #3	$130.99	12.288%	$147.0861	$147.09	$147.10	$147.10
Purchase #4	$150.66	9.435%	$164.8748	$164.87	$164.85	$164.90
Purchase #5	$39.92	6.403%	$42.4761	$42.48	$42.50	$42.50
Purchase #6	$175.78	13.168%	$198.9267	$198.93	$198.95	$198.90
Purchase #7	$156.67	3.501%	$162.155	$162.16	$162.15	$162.20
7 purchase totals =	$871.22		$951.5289	$951.54	$951.55	$951.60