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	$88.82	12.318%	$99.7608	$99.76	$99.75	$99.80
Purchase #2	$169.33	7.333%	$181.747	$181.75	$181.75	$181.70
Purchase #3	$206.94	5.120%	$217.5353	$217.54	$217.55	$217.50
Purchase #4	$47.92	10.300%	$52.8558	$52.86	$52.85	$52.90
Purchase #5	$217.43	7.457%	$233.6438	$233.64	$233.65	$233.60
Purchase #6	$95.92	6.490%	$102.1452	$102.15	$102.15	$102.10
Purchase #7	$229.64	13.801%	$261.3326	$261.33	$261.35	$261.30
7 purchase totals =	$1,056.00		$1,149.0205	$1,149.03	$1,149.05	$1,148.90