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	$83.37	3.561%	$86.3388	$86.34	$86.35	$86.30
Purchase #2	$52.48	12.234%	$58.9004	$58.90	$58.90	$58.90
Purchase #3	$59.97	11.656%	$66.9601	$66.96	$66.95	$67.00
Purchase #4	$192.61	9.420%	$210.7539	$210.75	$210.75	$210.80
Purchase #5	$213.95	13.478%	$242.7862	$242.79	$242.80	$242.80
Purchase #6	$172.73	8.562%	$187.5191	$187.52	$187.50	$187.50
Purchase #7	$81.46	9.384%	$89.1042	$89.10	$89.10	$89.10
7 purchase totals =	$856.57		$942.3627	$942.36	$942.35	$942.40