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	$38.84	6.371%	$41.3145	$41.31	$41.30	$41.30
Purchase #2	$186.48	5.857%	$197.4021	$197.40	$197.40	$197.40
Purchase #3	$76.98	4.692%	$80.5919	$80.59	$80.60	$80.60
Purchase #4	$194.76	13.359%	$220.778	$220.78	$220.80	$220.80
Purchase #5	$73.36	12.764%	$82.7237	$82.72	$82.70	$82.70
Purchase #6	$38.42	10.511%	$42.4583	$42.46	$42.45	$42.50
Purchase #7	$89.39	11.598%	$99.7575	$99.76	$99.75	$99.80
7 purchase totals =	$698.23		$765.0260	$765.02	$765.00	$765.10