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	$112.57	13.437%	$127.696	$127.70	$127.70	$127.70
Purchase #2	$227.47	13.774%	$258.8017	$258.80	$258.80	$258.80
Purchase #3	$148.51	9.545%	$162.6853	$162.69	$162.70	$162.70
Purchase #4	$121.82	8.211%	$131.8226	$131.82	$131.80	$131.80
Purchase #5	$41.91	11.580%	$46.7632	$46.76	$46.75	$46.80
Purchase #6	$50.50	7.557%	$54.3163	$54.32	$54.30	$54.30
Purchase #7	$202.39	8.535%	$219.664	$219.66	$219.65	$219.70
7 purchase totals =	$905.17		$1,001.7491	$1,001.75	$1,001.70	$1,001.80