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	$215.88	3.427%	$223.2782	$223.28	$223.30	$223.30
Purchase #2	$24.47	10.418%	$27.0193	$27.02	$27.00	$27.00
Purchase #3	$32.63	13.780%	$37.1264	$37.13	$37.15	$37.10
Purchase #4	$105.79	10.259%	$116.643	$116.64	$116.65	$116.60
Purchase #5	$119.63	12.770%	$134.9068	$134.91	$134.90	$134.90
Purchase #6	$18.94	3.524%	$19.6074	$19.61	$19.60	$19.60
Purchase #7	$59.78	11.391%	$66.5895	$66.59	$66.60	$66.60
7 purchase totals =	$577.12		$625.1706	$625.18	$625.20	$625.10