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	$102.32	7.153%	$109.6389	$109.64	$109.65	$109.60
Purchase #2	$210.76	5.627%	$222.6195	$222.62	$222.60	$222.60
Purchase #3	$61.37	10.751%	$67.9679	$67.97	$67.95	$68.00
Purchase #4	$53.45	4.593%	$55.905	$55.91	$55.90	$55.90
Purchase #5	$66.79	8.324%	$72.3496	$72.35	$72.35	$72.30
Purchase #6	$105.62	3.468%	$109.2829	$109.28	$109.30	$109.30
Purchase #7	$87.66	7.122%	$93.9031	$93.90	$93.90	$93.90
7 purchase totals =	$687.97		$731.6669	$731.67	$731.65	$731.60