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	$234.52	8.546%	$254.5621	$254.56	$254.55	$254.60
Purchase #2	$175.32	6.809%	$187.2575	$187.26	$187.25	$187.30
Purchase #3	$45.67	7.349%	$49.0263	$49.03	$49.05	$49.00
Purchase #4	$80.76	11.324%	$89.9053	$89.91	$89.90	$89.90
Purchase #5	$78.92	5.783%	$83.4839	$83.48	$83.50	$83.50
Purchase #6	$203.33	13.491%	$230.7613	$230.76	$230.75	$230.80
Purchase #7	$125.28	5.192%	$131.7845	$131.78	$131.80	$131.80
7 purchase totals =	$943.80		$1,026.7809	$1,026.78	$1,026.80	$1,026.90