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	$159.81	9.591%	$175.1374	$175.14	$175.15	$175.10
Purchase #2	$36.66	12.616%	$41.285	$41.29	$41.30	$41.30
Purchase #3	$100.69	3.713%	$104.4286	$104.43	$104.45	$104.40
Purchase #4	$130.99	13.245%	$148.3396	$148.34	$148.35	$148.30
Purchase #5	$82.91	9.191%	$90.5303	$90.53	$90.55	$90.50
Purchase #6	$31.83	9.476%	$34.8462	$34.85	$34.85	$34.80
Purchase #7	$87.91	13.608%	$99.8728	$99.87	$99.85	$99.90
7 purchase totals =	$630.80		$694.4399	$694.45	$694.50	$694.30