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	$70.63	9.851%	$77.5878	$77.59	$77.60	$77.60
Purchase #2	$21.83	10.784%	$24.1841	$24.18	$24.20	$24.20
Purchase #3	$13.32	4.114%	$13.868	$13.87	$13.85	$13.90
Purchase #4	$50.78	4.857%	$53.2464	$53.25	$53.25	$53.20
Purchase #5	$43.49	7.141%	$46.5956	$46.60	$46.60	$46.60
Purchase #6	$199.41	12.307%	$223.9514	$223.95	$223.95	$224.00
Purchase #7	$15.27	10.415%	$16.8604	$16.86	$16.85	$16.90
7 purchase totals =	$414.73		$456.2937	$456.30	$456.30	$456.40