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	$96.46	10.143%	$106.2439	$106.24	$106.25	$106.20
Purchase #2	$95.89	9.752%	$105.2412	$105.24	$105.25	$105.20
Purchase #3	$162.43	3.331%	$167.8405	$167.84	$167.85	$167.80
Purchase #4	$28.42	12.345%	$31.9284	$31.93	$31.95	$31.90
Purchase #5	$123.82	3.613%	$128.2936	$128.29	$128.30	$128.30
Purchase #6	$202.34	13.158%	$228.9639	$228.96	$228.95	$229.00
Purchase #7	$160.85	12.354%	$180.7214	$180.72	$180.70	$180.70
7 purchase totals =	$870.21		$949.2329	$949.22	$949.25	$949.10