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	$194.80	13.588%	$221.2694	$221.27	$221.25	$221.30
Purchase #2	$77.57	6.672%	$82.7455	$82.75	$82.75	$82.70
Purchase #3	$175.58	12.186%	$196.9762	$196.98	$197.00	$197.00
Purchase #4	$100.43	4.841%	$105.2918	$105.29	$105.30	$105.30
Purchase #5	$157.56	8.714%	$171.2898	$171.29	$171.30	$171.30
Purchase #6	$176.92	9.281%	$193.3399	$193.34	$193.35	$193.30
Purchase #7	$151.50	3.277%	$156.4647	$156.46	$156.45	$156.50
7 purchase totals =	$1,034.36		$1,127.3773	$1,127.38	$1,127.40	$1,127.40