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	$83.27	11.349%	$92.7203	$92.72	$92.70	$92.70
Purchase #2	$109.79	4.589%	$114.8283	$114.83	$114.85	$114.80
Purchase #3	$112.52	3.572%	$116.5392	$116.54	$116.55	$116.50
Purchase #4	$152.45	9.519%	$166.9617	$166.96	$166.95	$167.00
Purchase #5	$122.71	5.830%	$129.864	$129.86	$129.85	$129.90
Purchase #6	$90.57	7.864%	$97.6924	$97.69	$97.70	$97.70
Purchase #7	$114.83	3.547%	$118.903	$118.90	$118.90	$118.90
7 purchase totals =	$786.14		$837.5089	$837.50	$837.50	$837.50