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	$112.25	11.793%	$125.4876	$125.49	$125.50	$125.50
Purchase #2	$48.71	12.628%	$54.8611	$54.86	$54.85	$54.90
Purchase #3	$231.64	10.577%	$256.1406	$256.14	$256.15	$256.10
Purchase #4	$151.51	11.216%	$168.5034	$168.50	$168.50	$168.50
Purchase #5	$92.78	12.655%	$104.5213	$104.52	$104.50	$104.50
Purchase #6	$34.26	7.289%	$36.7572	$36.76	$36.75	$36.80
Purchase #7	$243.54	10.429%	$268.9388	$268.94	$268.95	$268.90
7 purchase totals =	$914.69		$1,015.2100	$1,015.21	$1,015.20	$1,015.20