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	$181.77	6.454%	$193.5014	$193.50	$193.50	$193.50
Purchase #2	$143.81	12.691%	$162.0609	$162.06	$162.05	$162.10
Purchase #3	$10.59	6.668%	$11.2961	$11.30	$11.30	$11.30
Purchase #4	$40.37	7.511%	$43.4022	$43.40	$43.40	$43.40
Purchase #5	$34.44	8.675%	$37.4277	$37.43	$37.45	$37.40
Purchase #6	$51.37	10.339%	$56.6811	$56.68	$56.70	$56.70
Purchase #7	$26.75	5.858%	$28.317	$28.32	$28.30	$28.30
7 purchase totals =	$489.10		$532.6864	$532.69	$532.70	$532.70