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	$196.72	13.687%	$223.6451	$223.65	$223.65	$223.60
Purchase #2	$90.31	12.347%	$101.4606	$101.46	$101.45	$101.50
Purchase #3	$238.88	12.130%	$267.8561	$267.86	$267.85	$267.90
Purchase #4	$181.45	13.698%	$206.305	$206.31	$206.30	$206.30
Purchase #5	$66.69	11.805%	$74.5628	$74.56	$74.55	$74.60
Purchase #6	$73.65	11.495%	$82.1161	$82.12	$82.10	$82.10
Purchase #7	$11.37	4.259%	$11.8542	$11.85	$11.85	$11.90
7 purchase totals =	$859.07		$967.7999	$967.81	$967.75	$967.90