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	$41.76	7.382%	$44.8427	$44.84	$44.85	$44.80
Purchase #2	$203.60	9.130%	$222.1887	$222.19	$222.20	$222.20
Purchase #3	$38.71	3.773%	$40.1705	$40.17	$40.15	$40.20
Purchase #4	$147.57	3.469%	$152.6892	$152.69	$152.70	$152.70
Purchase #5	$241.68	13.294%	$273.8089	$273.81	$273.80	$273.80
Purchase #6	$41.32	9.832%	$45.3826	$45.38	$45.40	$45.40
Purchase #7	$220.63	3.809%	$229.0338	$229.03	$229.05	$229.00
7 purchase totals =	$935.27		$1,008.1164	$1,008.11	$1,008.15	$1,008.10