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	$166.60	3.146%	$171.8412	$171.84	$171.85	$171.80
Purchase #2	$107.38	12.448%	$120.7467	$120.75	$120.75	$120.70
Purchase #3	$209.93	9.501%	$229.8754	$229.88	$229.90	$229.90
Purchase #4	$15.56	13.196%	$17.6133	$17.61	$17.60	$17.60
Purchase #5	$203.60	5.790%	$215.3884	$215.39	$215.40	$215.40
Purchase #6	$163.96	12.604%	$184.6255	$184.63	$184.65	$184.60
Purchase #7	$69.44	10.104%	$76.4562	$76.46	$76.45	$76.50
7 purchase totals =	$936.47		$1,016.5467	$1,016.56	$1,016.60	$1,016.50