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	$131.31	4.250%	$136.8907	$136.89	$136.90	$136.90
Purchase #2	$49.91	11.795%	$55.7969	$55.80	$55.80	$55.80
Purchase #3	$64.48	12.211%	$72.3537	$72.35	$72.35	$72.40
Purchase #4	$232.43	5.287%	$244.7186	$244.72	$244.70	$244.70
Purchase #5	$116.43	12.526%	$131.014	$131.01	$131.00	$131.00
Purchase #6	$229.89	5.403%	$242.311	$242.31	$242.30	$242.30
Purchase #7	$89.89	11.661%	$100.3721	$100.37	$100.35	$100.40
7 purchase totals =	$914.34		$983.4570	$983.45	$983.40	$983.50