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	$205.29	4.786%	$215.1152	$215.12	$215.10	$215.10
Purchase #2	$223.33	3.518%	$231.1867	$231.19	$231.20	$231.20
Purchase #3	$79.39	7.372%	$85.2426	$85.24	$85.25	$85.20
Purchase #4	$124.57	13.602%	$141.514	$141.51	$141.50	$141.50
Purchase #5	$242.28	13.776%	$275.6565	$275.66	$275.65	$275.70
Purchase #6	$159.73	11.138%	$177.5207	$177.52	$177.50	$177.50
Purchase #7	$19.69	9.871%	$21.6336	$21.63	$21.65	$21.60
7 purchase totals =	$1,054.28		$1,147.8693	$1,147.87	$1,147.85	$1,147.80