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	$118.56	10.837%	$131.4083	$131.41	$131.40	$131.40
Purchase #2	$245.53	7.194%	$263.1934	$263.19	$263.20	$263.20
Purchase #3	$207.50	10.312%	$228.8974	$228.90	$228.90	$228.90
Purchase #4	$161.46	7.160%	$173.0205	$173.02	$173.00	$173.00
Purchase #5	$91.36	8.464%	$99.0927	$99.09	$99.10	$99.10
Purchase #6	$97.59	13.185%	$110.4572	$110.46	$110.45	$110.50
Purchase #7	$36.31	12.726%	$40.9308	$40.93	$40.95	$40.90
7 purchase totals =	$958.31		$1,047.0003	$1,047.00	$1,047.00	$1,047.00