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	$213.42	12.503%	$240.1039	$240.10	$240.10	$240.10
Purchase #2	$194.92	12.448%	$219.1836	$219.18	$219.20	$219.20
Purchase #3	$116.72	6.129%	$123.8738	$123.87	$123.85	$123.90
Purchase #4	$203.51	7.662%	$219.1029	$219.10	$219.10	$219.10
Purchase #5	$162.53	13.415%	$184.3334	$184.33	$184.35	$184.30
Purchase #6	$33.89	11.368%	$37.7426	$37.74	$37.75	$37.70
Purchase #7	$116.44	9.480%	$127.4785	$127.48	$127.50	$127.50
7 purchase totals =	$1,041.43		$1,151.8187	$1,151.80	$1,151.85	$1,151.80