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	$167.79	6.471%	$178.6477	$178.65	$178.65	$178.60
Purchase #2	$96.55	9.392%	$105.618	$105.62	$105.60	$105.60
Purchase #3	$183.25	4.300%	$191.1298	$191.13	$191.15	$191.10
Purchase #4	$93.63	9.772%	$102.7795	$102.78	$102.80	$102.80
Purchase #5	$238.31	9.504%	$260.959	$260.96	$260.95	$261.00
Purchase #6	$75.34	4.303%	$78.5819	$78.58	$78.60	$78.60
Purchase #7	$41.86	10.802%	$46.3817	$46.38	$46.40	$46.40
7 purchase totals =	$896.73		$964.0976	$964.10	$964.15	$964.10