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	$124.63	4.522%	$130.2658	$130.27	$130.25	$130.30
Purchase #2	$104.34	7.837%	$112.5171	$112.52	$112.50	$112.50
Purchase #3	$18.65	9.105%	$20.3481	$20.35	$20.35	$20.30
Purchase #4	$188.32	10.811%	$208.6793	$208.68	$208.70	$208.70
Purchase #5	$31.75	13.291%	$35.9699	$35.97	$35.95	$36.00
Purchase #6	$182.31	9.130%	$198.9549	$198.95	$198.95	$199.00
Purchase #7	$53.49	11.594%	$59.6916	$59.69	$59.70	$59.70
7 purchase totals =	$703.49		$766.4267	$766.43	$766.40	$766.50