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	$82.46	12.135%	$92.4665	$92.47	$92.45	$92.50
Purchase #2	$210.39	12.419%	$236.5183	$236.52	$236.50	$236.50
Purchase #3	$83.52	6.663%	$89.0849	$89.08	$89.10	$89.10
Purchase #4	$22.97	7.758%	$24.752	$24.75	$24.75	$24.80
Purchase #5	$52.28	13.602%	$59.3911	$59.39	$59.40	$59.40
Purchase #6	$55.48	7.398%	$59.5844	$59.58	$59.60	$59.60
Purchase #7	$195.86	3.128%	$201.9865	$201.99	$202.00	$202.00
7 purchase totals =	$702.96		$763.7837	$763.78	$763.80	$763.90