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	$223.70	11.200%	$248.7544	$248.75	$248.75	$248.80
Purchase #2	$15.98	5.213%	$16.813	$16.81	$16.80	$16.80
Purchase #3	$153.43	9.738%	$168.371	$168.37	$168.35	$168.40
Purchase #4	$143.76	6.345%	$152.8816	$152.88	$152.90	$152.90
Purchase #5	$174.33	5.456%	$183.8414	$183.84	$183.85	$183.80
Purchase #6	$177.42	12.270%	$199.1894	$199.19	$199.20	$199.20
Purchase #7	$98.31	13.484%	$111.5661	$111.57	$111.55	$111.60
7 purchase totals =	$986.93		$1,081.4169	$1,081.41	$1,081.40	$1,081.50