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	$86.83	3.437%	$89.8143	$89.81	$89.80	$89.80
Purchase #2	$193.40	11.112%	$214.8906	$214.89	$214.90	$214.90
Purchase #3	$111.51	7.176%	$119.512	$119.51	$119.50	$119.50
Purchase #4	$147.30	5.529%	$155.4442	$155.44	$155.45	$155.40
Purchase #5	$62.57	13.823%	$71.2191	$71.22	$71.20	$71.20
Purchase #6	$36.88	5.307%	$38.8372	$38.84	$38.85	$38.80
Purchase #7	$119.55	4.803%	$125.292	$125.29	$125.30	$125.30
7 purchase totals =	$758.04		$815.0094	$815.00	$815.00	$814.90