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	$224.38	4.705%	$234.9371	$234.94	$234.95	$234.90
Purchase #2	$216.44	13.116%	$244.8283	$244.83	$244.85	$244.80
Purchase #3	$97.49	7.834%	$105.1274	$105.13	$105.15	$105.10
Purchase #4	$231.84	9.466%	$253.786	$253.79	$253.80	$253.80
Purchase #5	$152.94	6.226%	$162.462	$162.46	$162.45	$162.50
Purchase #6	$29.76	7.217%	$31.9078	$31.91	$31.90	$31.90
Purchase #7	$140.69	3.171%	$145.1513	$145.15	$145.15	$145.20
7 purchase totals =	$1,093.54		$1,178.1999	$1,178.21	$1,178.25	$1,178.20