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	$112.36	4.174%	$117.0499	$117.05	$117.05	$117.00
Purchase #2	$43.93	4.347%	$45.8396	$45.84	$45.85	$45.80
Purchase #3	$172.66	13.824%	$196.5285	$196.53	$196.55	$196.50
Purchase #4	$43.95	5.704%	$46.4569	$46.46	$46.45	$46.50
Purchase #5	$210.70	5.306%	$221.8797	$221.88	$221.90	$221.90
Purchase #6	$89.47	13.793%	$101.8106	$101.81	$101.80	$101.80
Purchase #7	$33.65	12.350%	$37.8058	$37.81	$37.80	$37.80
7 purchase totals =	$706.72		$767.3710	$767.38	$767.40	$767.30