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	$105.31	12.865%	$118.8581	$118.86	$118.85	$118.90
Purchase #2	$191.95	9.539%	$210.2601	$210.26	$210.25	$210.30
Purchase #3	$178.56	11.396%	$198.9087	$198.91	$198.90	$198.90
Purchase #4	$31.39	7.825%	$33.8463	$33.85	$33.85	$33.80
Purchase #5	$231.90	10.333%	$255.8622	$255.86	$255.85	$255.90
Purchase #6	$152.94	4.859%	$160.3714	$160.37	$160.35	$160.40
Purchase #7	$22.25	7.597%	$23.9403	$23.94	$23.95	$23.90
7 purchase totals =	$914.30		$1,002.0471	$1,002.05	$1,002.00	$1,002.10