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	$129.96	11.193%	$144.5064	$144.51	$144.50	$144.50
Purchase #2	$67.72	5.315%	$71.3193	$71.32	$71.30	$71.30
Purchase #3	$238.82	6.851%	$255.1816	$255.18	$255.20	$255.20
Purchase #4	$46.95	9.265%	$51.2999	$51.30	$51.30	$51.30
Purchase #5	$15.97	3.148%	$16.4727	$16.47	$16.45	$16.50
Purchase #6	$245.55	7.735%	$264.5433	$264.54	$264.55	$264.50
Purchase #7	$212.41	9.195%	$231.9411	$231.94	$231.95	$231.90
7 purchase totals =	$957.38		$1,035.2643	$1,035.26	$1,035.25	$1,035.20