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	$53.99	12.874%	$60.9407	$60.94	$60.95	$60.90
Purchase #2	$47.89	4.142%	$49.8736	$49.87	$49.85	$49.90
Purchase #3	$181.42	9.380%	$198.4372	$198.44	$198.45	$198.40
Purchase #4	$129.50	6.495%	$137.911	$137.91	$137.90	$137.90
Purchase #5	$58.90	11.125%	$65.4526	$65.45	$65.45	$65.50
Purchase #6	$125.61	8.852%	$136.729	$136.73	$136.75	$136.70
Purchase #7	$70.38	12.174%	$78.9481	$78.95	$78.95	$78.90
7 purchase totals =	$667.69		$728.2922	$728.29	$728.30	$728.20