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	$106.98	8.735%	$116.3247	$116.32	$116.30	$116.30
Purchase #2	$154.60	11.334%	$172.1224	$172.12	$172.10	$172.10
Purchase #3	$139.47	11.140%	$155.007	$155.01	$155.00	$155.00
Purchase #4	$41.76	4.476%	$43.6292	$43.63	$43.65	$43.60
Purchase #5	$127.42	7.150%	$136.5305	$136.53	$136.55	$136.50
Purchase #6	$197.76	11.190%	$219.8893	$219.89	$219.90	$219.90
Purchase #7	$156.96	10.836%	$173.9682	$173.97	$173.95	$174.00
7 purchase totals =	$924.95		$1,017.4713	$1,017.47	$1,017.45	$1,017.40