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	$198.86	13.152%	$225.0141	$225.01	$225.00	$225.00
Purchase #2	$111.25	3.281%	$114.9001	$114.90	$114.90	$114.90
Purchase #3	$186.46	6.462%	$198.509	$198.51	$198.50	$198.50
Purchase #4	$154.56	5.106%	$162.4518	$162.45	$162.45	$162.50
Purchase #5	$222.26	10.192%	$244.9127	$244.91	$244.90	$244.90
Purchase #6	$196.33	6.491%	$209.0738	$209.07	$209.05	$209.10
Purchase #7	$36.29	13.166%	$41.0679	$41.07	$41.05	$41.10
7 purchase totals =	$1,106.01		$1,195.9294	$1,195.92	$1,195.85	$1,196.00