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	$92.25	12.255%	$103.5552	$103.56	$103.55	$103.60
Purchase #2	$94.51	8.627%	$102.6634	$102.66	$102.65	$102.70
Purchase #3	$79.96	7.735%	$86.1449	$86.14	$86.15	$86.10
Purchase #4	$194.77	8.122%	$210.5892	$210.59	$210.60	$210.60
Purchase #5	$25.46	13.655%	$28.9366	$28.94	$28.95	$28.90
Purchase #6	$104.53	4.849%	$109.5987	$109.60	$109.60	$109.60
Purchase #7	$28.62	11.748%	$31.9823	$31.98	$32.00	$32.00
7 purchase totals =	$620.10		$673.4703	$673.47	$673.50	$673.50