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	$31.37	8.443%	$34.0186	$34.02	$34.00	$34.00
Purchase #2	$80.45	8.680%	$87.4331	$87.43	$87.45	$87.40
Purchase #3	$211.81	6.779%	$226.1686	$226.17	$226.15	$226.20
Purchase #4	$174.89	12.554%	$196.8457	$196.85	$196.85	$196.80
Purchase #5	$149.48	13.574%	$169.7704	$169.77	$169.75	$169.80
Purchase #6	$82.94	7.302%	$88.9963	$89.00	$89.00	$89.00
Purchase #7	$195.49	10.399%	$215.819	$215.82	$215.80	$215.80
7 purchase totals =	$926.43		$1,019.0517	$1,019.06	$1,019.00	$1,019.00