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	$236.69	7.402%	$254.2098	$254.21	$254.20	$254.20
Purchase #2	$63.57	11.537%	$70.9041	$70.90	$70.90	$70.90
Purchase #3	$219.73	6.136%	$233.2126	$233.21	$233.20	$233.20
Purchase #4	$101.85	7.699%	$109.6914	$109.69	$109.70	$109.70
Purchase #5	$37.40	7.156%	$40.0763	$40.08	$40.10	$40.10
Purchase #6	$105.36	10.270%	$116.1805	$116.18	$116.20	$116.20
Purchase #7	$236.50	13.802%	$269.1417	$269.14	$269.15	$269.10
7 purchase totals =	$1,001.10		$1,093.4164	$1,093.41	$1,093.45	$1,093.40