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	$157.73	3.230%	$162.8247	$162.82	$162.80	$162.80
Purchase #2	$55.84	6.712%	$59.588	$59.59	$59.60	$59.60
Purchase #3	$89.64	12.631%	$100.9624	$100.96	$100.95	$101.00
Purchase #4	$31.92	13.865%	$36.3457	$36.35	$36.35	$36.30
Purchase #5	$126.75	7.737%	$136.5566	$136.56	$136.55	$136.60
Purchase #6	$215.87	13.644%	$245.3233	$245.32	$245.30	$245.30
Purchase #7	$192.26	11.744%	$214.839	$214.84	$214.85	$214.80
7 purchase totals =	$870.01		$956.4397	$956.44	$956.40	$956.40