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	$145.36	11.514%	$162.0968	$162.10	$162.10	$162.10
Purchase #2	$6.45	7.510%	$6.9344	$6.93	$6.95	$6.90
Purchase #3	$250.83	4.677%	$262.5613	$262.56	$262.55	$262.60
Purchase #4	$233.85	10.712%	$258.9	$258.90	$258.90	$258.90
Purchase #5	$246.54	7.574%	$265.2129	$265.21	$265.20	$265.20
Purchase #6	$150.72	10.150%	$166.0181	$166.02	$166.00	$166.00
Purchase #7	$159.45	8.393%	$172.8326	$172.83	$172.85	$172.80
7 purchase totals =	$1,193.20		$1,294.5561	$1,294.55	$1,294.55	$1,294.50