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	$207.51	12.406%	$233.2537	$233.25	$233.25	$233.30
Purchase #2	$121.89	12.669%	$137.3322	$137.33	$137.35	$137.30
Purchase #3	$158.50	13.377%	$179.7025	$179.70	$179.70	$179.70
Purchase #4	$179.59	7.204%	$192.5277	$192.53	$192.55	$192.50
Purchase #5	$28.32	9.825%	$31.1024	$31.10	$31.10	$31.10
Purchase #6	$192.97	4.103%	$200.8876	$200.89	$200.90	$200.90
Purchase #7	$103.52	4.873%	$108.5645	$108.56	$108.55	$108.60
7 purchase totals =	$992.30		$1,083.3706	$1,083.36	$1,083.40	$1,083.40