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	$82.81	7.600%	$89.1036	$89.10	$89.10	$89.10
Purchase #2	$20.34	7.390%	$21.8431	$21.84	$21.85	$21.80
Purchase #3	$59.25	4.475%	$61.9014	$61.90	$61.90	$61.90
Purchase #4	$155.49	5.716%	$164.3778	$164.38	$164.40	$164.40
Purchase #5	$163.26	4.824%	$171.1357	$171.14	$171.15	$171.10
Purchase #6	$235.80	6.395%	$250.8794	$250.88	$250.90	$250.90
Purchase #7	$43.68	5.761%	$46.1964	$46.20	$46.20	$46.20
7 purchase totals =	$760.63		$805.4374	$805.44	$805.50	$805.40