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	$55.55	6.270%	$59.033	$59.03	$59.05	$59.00
Purchase #2	$192.36	9.647%	$210.917	$210.92	$210.90	$210.90
Purchase #3	$39.90	10.302%	$44.0105	$44.01	$44.00	$44.00
Purchase #4	$217.86	7.286%	$233.7333	$233.73	$233.75	$233.70
Purchase #5	$96.93	8.400%	$105.0721	$105.07	$105.05	$105.10
Purchase #6	$6.33	12.559%	$7.125	$7.13	$7.15	$7.10
Purchase #7	$171.96	11.716%	$192.1068	$192.11	$192.10	$192.10
7 purchase totals =	$780.89		$851.9977	$852.00	$852.00	$851.90