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	$24.37	5.849%	$25.7954	$25.80	$25.80	$25.80
Purchase #2	$47.68	11.167%	$53.0044	$53.00	$53.00	$53.00
Purchase #3	$96.59	7.626%	$103.956	$103.96	$103.95	$104.00
Purchase #4	$51.46	3.725%	$53.3769	$53.38	$53.40	$53.40
Purchase #5	$188.27	3.795%	$195.4148	$195.41	$195.40	$195.40
Purchase #6	$98.73	6.697%	$105.3419	$105.34	$105.35	$105.30
Purchase #7	$30.72	12.168%	$34.458	$34.46	$34.45	$34.50
7 purchase totals =	$537.82		$571.3474	$571.35	$571.35	$571.40