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	$31.69	13.673%	$36.023	$36.02	$36.00	$36.00
Purchase #2	$90.85	10.710%	$100.58	$100.58	$100.60	$100.60
Purchase #3	$241.30	13.321%	$273.4436	$273.44	$273.45	$273.40
Purchase #4	$222.96	4.817%	$233.7	$233.70	$233.70	$233.70
Purchase #5	$102.89	6.341%	$109.4143	$109.41	$109.40	$109.40
Purchase #6	$172.34	5.575%	$181.948	$181.95	$181.95	$181.90
Purchase #7	$104.96	10.842%	$116.3398	$116.34	$116.35	$116.30
7 purchase totals =	$966.99		$1,051.4487	$1,051.44	$1,051.45	$1,051.30