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	$45.60	6.104%	$48.3834	$48.38	$48.40	$48.40
Purchase #2	$9.86	10.668%	$10.9119	$10.91	$10.90	$10.90
Purchase #3	$196.54	5.111%	$206.5852	$206.59	$206.60	$206.60
Purchase #4	$189.90	9.488%	$207.9177	$207.92	$207.90	$207.90
Purchase #5	$33.29	12.512%	$37.4552	$37.46	$37.45	$37.50
Purchase #6	$75.29	9.835%	$82.6948	$82.69	$82.70	$82.70
Purchase #7	$65.52	9.289%	$71.6062	$71.61	$71.60	$71.60
7 purchase totals =	$616.00		$665.5544	$665.56	$665.55	$665.60