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	$190.47	3.382%	$196.9117	$196.91	$196.90	$196.90
Purchase #2	$55.95	13.209%	$63.3404	$63.34	$63.35	$63.30
Purchase #3	$199.94	5.296%	$210.5288	$210.53	$210.55	$210.50
Purchase #4	$52.72	11.874%	$58.98	$58.98	$59.00	$59.00
Purchase #5	$164.82	11.789%	$184.2506	$184.25	$184.25	$184.30
Purchase #6	$33.55	10.508%	$37.0754	$37.08	$37.10	$37.10
Purchase #7	$80.31	4.239%	$83.7143	$83.71	$83.70	$83.70
7 purchase totals =	$777.76		$834.8012	$834.80	$834.85	$834.80