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	$48.93	10.835%	$54.2316	$54.23	$54.25	$54.20
Purchase #2	$73.87	10.838%	$81.876	$81.88	$81.90	$81.90
Purchase #3	$145.59	3.847%	$151.1908	$151.19	$151.20	$151.20
Purchase #4	$171.90	9.838%	$188.8115	$188.81	$188.80	$188.80
Purchase #5	$97.51	13.818%	$110.9839	$110.98	$111.00	$111.00
Purchase #6	$29.51	11.259%	$32.8325	$32.83	$32.85	$32.80
Purchase #7	$200.99	13.354%	$227.8302	$227.83	$227.85	$227.80
7 purchase totals =	$768.30		$847.7565	$847.75	$847.85	$847.70