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	$160.36	7.663%	$172.6484	$172.65	$172.65	$172.60
Purchase #2	$141.47	13.257%	$160.2247	$160.22	$160.20	$160.20
Purchase #3	$241.43	9.492%	$264.3465	$264.35	$264.35	$264.30
Purchase #4	$129.75	12.516%	$145.9895	$145.99	$146.00	$146.00
Purchase #5	$39.57	5.273%	$41.6565	$41.66	$41.65	$41.70
Purchase #6	$36.70	10.510%	$40.5572	$40.56	$40.55	$40.60
Purchase #7	$191.94	4.631%	$200.8287	$200.83	$200.85	$200.80
7 purchase totals =	$941.22		$1,026.2515	$1,026.26	$1,026.25	$1,026.20