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	$96.44	5.735%	$101.9708	$101.97	$101.95	$102.00
Purchase #2	$31.59	10.330%	$34.8532	$34.85	$34.85	$34.90
Purchase #3	$199.86	5.514%	$210.8803	$210.88	$210.90	$210.90
Purchase #4	$86.37	3.400%	$89.3066	$89.31	$89.30	$89.30
Purchase #5	$181.48	10.340%	$200.245	$200.25	$200.25	$200.20
Purchase #6	$128.45	11.451%	$143.1588	$143.16	$143.15	$143.20
Purchase #7	$133.46	4.295%	$139.1921	$139.19	$139.20	$139.20
7 purchase totals =	$857.65		$919.6068	$919.61	$919.60	$919.70