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	$211.57	3.619%	$219.2267	$219.23	$219.25	$219.20
Purchase #2	$60.43	11.636%	$67.4616	$67.46	$67.45	$67.50
Purchase #3	$56.87	3.796%	$59.0288	$59.03	$59.05	$59.00
Purchase #4	$116.92	13.172%	$132.3207	$132.32	$132.30	$132.30
Purchase #5	$236.85	11.320%	$263.6614	$263.66	$263.65	$263.70
Purchase #6	$50.64	12.345%	$56.8915	$56.89	$56.90	$56.90
Purchase #7	$115.82	3.473%	$119.8424	$119.84	$119.85	$119.80
7 purchase totals =	$849.10		$918.4331	$918.43	$918.45	$918.40