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	$129.29	10.714%	$143.1421	$143.14	$143.15	$143.10
Purchase #2	$151.85	10.840%	$168.3105	$168.31	$168.30	$168.30
Purchase #3	$16.50	5.421%	$17.3945	$17.39	$17.40	$17.40
Purchase #4	$174.67	13.786%	$198.75	$198.75	$198.75	$198.80
Purchase #5	$43.33	10.699%	$47.9659	$47.97	$47.95	$48.00
Purchase #6	$144.69	12.333%	$162.5346	$162.53	$162.55	$162.50
Purchase #7	$71.47	12.593%	$80.4702	$80.47	$80.45	$80.50
7 purchase totals =	$731.80		$818.5678	$818.56	$818.55	$818.60