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	$61.87	5.197%	$65.0854	$65.09	$65.10	$65.10
Purchase #2	$229.74	11.377%	$255.8775	$255.88	$255.90	$255.90
Purchase #3	$130.99	4.291%	$136.6108	$136.61	$136.60	$136.60
Purchase #4	$142.30	7.743%	$153.3183	$153.32	$153.30	$153.30
Purchase #5	$195.30	11.812%	$218.3688	$218.37	$218.35	$218.40
Purchase #6	$132.98	9.731%	$145.9203	$145.92	$145.90	$145.90
Purchase #7	$39.31	5.173%	$41.3435	$41.34	$41.35	$41.30
7 purchase totals =	$932.49		$1,016.5246	$1,016.53	$1,016.50	$1,016.50