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	$134.45	5.119%	$141.3325	$141.33	$141.35	$141.30
Purchase #2	$7.45	10.494%	$8.2318	$8.23	$8.25	$8.20
Purchase #3	$218.99	9.698%	$240.2277	$240.23	$240.25	$240.20
Purchase #4	$219.41	6.402%	$233.4566	$233.46	$233.45	$233.50
Purchase #5	$40.71	11.479%	$45.3831	$45.38	$45.40	$45.40
Purchase #6	$248.45	3.812%	$257.9209	$257.92	$257.90	$257.90
Purchase #7	$127.60	4.667%	$133.5551	$133.56	$133.55	$133.60
7 purchase totals =	$997.06		$1,060.1077	$1,060.11	$1,060.15	$1,060.10