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	$11.25	9.277%	$12.2937	$12.29	$12.30	$12.30
Purchase #2	$108.80	3.452%	$112.5558	$112.56	$112.55	$112.60
Purchase #3	$86.40	3.331%	$89.278	$89.28	$89.30	$89.30
Purchase #4	$162.39	7.614%	$174.7544	$174.75	$174.75	$174.80
Purchase #5	$153.65	4.712%	$160.89	$160.89	$160.90	$160.90
Purchase #6	$76.75	12.177%	$86.0958	$86.10	$86.10	$86.10
Purchase #7	$65.78	5.363%	$69.3078	$69.31	$69.30	$69.30
7 purchase totals =	$665.02		$705.1755	$705.18	$705.20	$705.30