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	$242.27	3.580%	$250.9433	$250.94	$250.95	$250.90
Purchase #2	$144.53	10.259%	$159.3573	$159.36	$159.35	$159.40
Purchase #3	$214.46	11.179%	$238.4345	$238.43	$238.45	$238.40
Purchase #4	$175.39	3.458%	$181.455	$181.46	$181.45	$181.50
Purchase #5	$57.54	12.164%	$64.5392	$64.54	$64.55	$64.50
Purchase #6	$81.88	7.769%	$88.2413	$88.24	$88.25	$88.20
Purchase #7	$62.70	6.173%	$66.5705	$66.57	$66.55	$66.60
7 purchase totals =	$978.77		$1,049.5411	$1,049.54	$1,049.55	$1,049.50