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	$110.69	4.760%	$115.9588	$115.96	$115.95	$116.00
Purchase #2	$194.92	10.600%	$215.5815	$215.58	$215.60	$215.60
Purchase #3	$21.82	13.242%	$24.7094	$24.71	$24.70	$24.70
Purchase #4	$240.42	6.318%	$255.6097	$255.61	$255.60	$255.60
Purchase #5	$124.95	12.785%	$140.9249	$140.92	$140.90	$140.90
Purchase #6	$11.31	7.460%	$12.1537	$12.15	$12.15	$12.20
Purchase #7	$64.99	11.498%	$72.4626	$72.46	$72.45	$72.50
7 purchase totals =	$769.10		$837.4006	$837.39	$837.35	$837.50