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	$191.52	12.482%	$215.4255	$215.43	$215.45	$215.40
Purchase #2	$159.49	5.489%	$168.2444	$168.24	$168.25	$168.20
Purchase #3	$118.69	7.559%	$127.6618	$127.66	$127.65	$127.70
Purchase #4	$228.53	12.289%	$256.6141	$256.61	$256.60	$256.60
Purchase #5	$59.74	7.538%	$64.2432	$64.24	$64.25	$64.20
Purchase #6	$236.25	13.829%	$268.921	$268.92	$268.90	$268.90
Purchase #7	$29.93	7.703%	$32.2355	$32.24	$32.25	$32.20
7 purchase totals =	$1,024.15		$1,133.3455	$1,133.34	$1,133.35	$1,133.20