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	$63.81	11.283%	$71.0097	$71.01	$71.00	$71.00
Purchase #2	$73.49	8.436%	$79.6896	$79.69	$79.70	$79.70
Purchase #3	$94.25	5.339%	$99.282	$99.28	$99.30	$99.30
Purchase #4	$54.94	4.206%	$57.2508	$57.25	$57.25	$57.30
Purchase #5	$41.61	5.526%	$43.9094	$43.91	$43.90	$43.90
Purchase #6	$106.46	13.312%	$120.632	$120.63	$120.65	$120.60
Purchase #7	$181.45	6.637%	$193.4928	$193.49	$193.50	$193.50
7 purchase totals =	$616.01		$665.2663	$665.26	$665.30	$665.30