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	$130.92	4.718%	$137.0968	$137.10	$137.10	$137.10
Purchase #2	$40.54	7.306%	$43.5019	$43.50	$43.50	$43.50
Purchase #3	$167.41	10.293%	$184.6415	$184.64	$184.65	$184.60
Purchase #4	$68.82	5.580%	$72.6602	$72.66	$72.65	$72.70
Purchase #5	$219.32	7.570%	$235.9225	$235.92	$235.90	$235.90
Purchase #6	$126.54	4.284%	$131.961	$131.96	$131.95	$132.00
Purchase #7	$25.54	10.604%	$28.2483	$28.25	$28.25	$28.20
7 purchase totals =	$779.09		$834.0322	$834.03	$834.00	$834.00