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	$101.36	9.587%	$111.0774	$111.08	$111.10	$111.10
Purchase #2	$216.65	9.433%	$237.0866	$237.09	$237.10	$237.10
Purchase #3	$50.37	7.305%	$54.0495	$54.05	$54.05	$54.00
Purchase #4	$67.36	6.765%	$71.9169	$71.92	$71.90	$71.90
Purchase #5	$58.91	5.779%	$62.3144	$62.31	$62.30	$62.30
Purchase #6	$79.49	13.865%	$90.5113	$90.51	$90.50	$90.50
Purchase #7	$239.41	6.128%	$254.081	$254.08	$254.10	$254.10
7 purchase totals =	$813.55		$881.0371	$881.04	$881.05	$881.00