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	$105.32	6.508%	$112.1742	$112.17	$112.15	$112.20
Purchase #2	$88.81	12.296%	$99.7301	$99.73	$99.75	$99.70
Purchase #3	$119.69	8.166%	$129.4639	$129.46	$129.45	$129.50
Purchase #4	$249.73	3.779%	$259.1673	$259.17	$259.15	$259.20
Purchase #5	$21.36	7.296%	$22.9184	$22.92	$22.90	$22.90
Purchase #6	$219.31	10.154%	$241.5787	$241.58	$241.60	$241.60
Purchase #7	$131.55	5.695%	$139.0418	$139.04	$139.05	$139.00
7 purchase totals =	$935.77		$1,004.0744	$1,004.07	$1,004.05	$1,004.10