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	$181.53	8.183%	$196.3846	$196.38	$196.40	$196.40
Purchase #2	$229.29	12.582%	$258.1393	$258.14	$258.15	$258.10
Purchase #3	$28.50	10.763%	$31.5675	$31.57	$31.55	$31.60
Purchase #4	$173.66	11.259%	$193.2124	$193.21	$193.20	$193.20
Purchase #5	$132.68	13.255%	$150.2667	$150.27	$150.25	$150.30
Purchase #6	$223.61	10.611%	$247.3373	$247.34	$247.35	$247.30
Purchase #7	$87.46	13.822%	$99.5487	$99.55	$99.55	$99.50
7 purchase totals =	$1,056.73		$1,176.4565	$1,176.46	$1,176.45	$1,176.40