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	$168.87	4.444%	$176.3746	$176.37	$176.35	$176.40
Purchase #2	$173.93	9.576%	$190.5855	$190.59	$190.60	$190.60
Purchase #3	$20.31	10.147%	$22.3709	$22.37	$22.35	$22.40
Purchase #4	$222.69	4.610%	$232.956	$232.96	$232.95	$233.00
Purchase #5	$57.98	3.157%	$59.8104	$59.81	$59.80	$59.80
Purchase #6	$238.54	4.524%	$249.3315	$249.33	$249.35	$249.30
Purchase #7	$53.51	5.639%	$56.5274	$56.53	$56.55	$56.50
7 purchase totals =	$935.83		$987.9563	$987.96	$987.95	$988.00