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	$95.90	11.499%	$106.9275	$106.93	$106.95	$106.90
Purchase #2	$87.74	4.248%	$91.4672	$91.47	$91.45	$91.50
Purchase #3	$77.41	11.475%	$86.2928	$86.29	$86.30	$86.30
Purchase #4	$48.79	10.743%	$54.0315	$54.03	$54.05	$54.00
Purchase #5	$62.64	4.168%	$65.2508	$65.25	$65.25	$65.30
Purchase #6	$235.53	10.874%	$261.1415	$261.14	$261.15	$261.10
Purchase #7	$69.96	11.610%	$78.0824	$78.08	$78.10	$78.10
7 purchase totals =	$677.97		$743.1937	$743.19	$743.25	$743.20