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	$89.34	10.118%	$98.3794	$98.38	$98.40	$98.40
Purchase #2	$78.79	4.679%	$82.4766	$82.48	$82.50	$82.50
Purchase #3	$192.58	3.229%	$198.7984	$198.80	$198.80	$198.80
Purchase #4	$243.54	6.171%	$258.5689	$258.57	$258.55	$258.60
Purchase #5	$237.31	11.673%	$265.0112	$265.01	$265.00	$265.00
Purchase #6	$140.42	4.751%	$147.0914	$147.09	$147.10	$147.10
Purchase #7	$33.81	8.743%	$36.766	$36.77	$36.75	$36.80
7 purchase totals =	$1,015.79		$1,087.0919	$1,087.10	$1,087.10	$1,087.20