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	$51.74	5.161%	$54.4103	$54.41	$54.40	$54.40
Purchase #2	$110.32	11.873%	$123.4183	$123.42	$123.40	$123.40
Purchase #3	$153.70	7.627%	$165.4227	$165.42	$165.40	$165.40
Purchase #4	$249.57	9.713%	$273.8107	$273.81	$273.80	$273.80
Purchase #5	$89.51	3.417%	$92.5686	$92.57	$92.55	$92.60
Purchase #6	$204.38	9.735%	$224.2764	$224.28	$224.30	$224.30
Purchase #7	$69.58	7.159%	$74.5612	$74.56	$74.55	$74.60
7 purchase totals =	$928.80		$1,008.4682	$1,008.47	$1,008.40	$1,008.50