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	$105.46	5.525%	$111.2867	$111.29	$111.30	$111.30
Purchase #2	$130.43	4.686%	$136.5419	$136.54	$136.55	$136.50
Purchase #3	$162.37	10.549%	$179.4984	$179.50	$179.50	$179.50
Purchase #4	$41.92	6.820%	$44.7789	$44.78	$44.80	$44.80
Purchase #5	$131.73	7.419%	$141.503	$141.50	$141.50	$141.50
Purchase #6	$105.67	10.193%	$116.4409	$116.44	$116.45	$116.40
Purchase #7	$32.96	11.255%	$36.6696	$36.67	$36.65	$36.70
7 purchase totals =	$710.54		$766.7194	$766.72	$766.75	$766.70