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	$151.41	5.278%	$159.4014	$159.40	$159.40	$159.40
Purchase #2	$30.49	4.613%	$31.8965	$31.90	$31.90	$31.90
Purchase #3	$93.77	6.732%	$100.0826	$100.08	$100.10	$100.10
Purchase #4	$49.80	8.208%	$53.8876	$53.89	$53.90	$53.90
Purchase #5	$11.31	4.866%	$11.8603	$11.86	$11.85	$11.90
Purchase #6	$205.43	9.494%	$224.9335	$224.93	$224.95	$224.90
Purchase #7	$12.38	8.112%	$13.3843	$13.38	$13.40	$13.40
7 purchase totals =	$554.59		$595.4462	$595.44	$595.50	$595.50