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	$79.34	9.431%	$86.8226	$86.82	$86.80	$86.80
Purchase #2	$171.94	5.291%	$181.0373	$181.04	$181.05	$181.00
Purchase #3	$135.55	5.520%	$143.0324	$143.03	$143.05	$143.00
Purchase #4	$187.31	11.861%	$209.5268	$209.53	$209.55	$209.50
Purchase #5	$56.47	5.206%	$59.4098	$59.41	$59.40	$59.40
Purchase #6	$143.61	10.837%	$159.173	$159.17	$159.15	$159.20
Purchase #7	$104.76	11.184%	$116.4764	$116.48	$116.50	$116.50
7 purchase totals =	$878.98		$955.4783	$955.48	$955.50	$955.40