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	$238.95	13.300%	$270.7304	$270.73	$270.75	$270.70
Purchase #2	$171.38	4.160%	$178.5094	$178.51	$178.50	$178.50
Purchase #3	$57.98	13.189%	$65.627	$65.63	$65.65	$65.60
Purchase #4	$83.51	4.507%	$87.2738	$87.27	$87.25	$87.30
Purchase #5	$156.25	7.820%	$168.4688	$168.47	$168.45	$168.50
Purchase #6	$53.42	6.849%	$57.0787	$57.08	$57.10	$57.10
Purchase #7	$236.54	13.369%	$268.163	$268.16	$268.15	$268.20
7 purchase totals =	$998.03		$1,095.8511	$1,095.85	$1,095.85	$1,095.90