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	$183.36	4.429%	$191.481	$191.48	$191.50	$191.50
Purchase #2	$60.50	12.214%	$67.8895	$67.89	$67.90	$67.90
Purchase #3	$234.65	7.421%	$252.0634	$252.06	$252.05	$252.10
Purchase #4	$137.75	3.207%	$142.1676	$142.17	$142.15	$142.20
Purchase #5	$205.83	8.528%	$223.3832	$223.38	$223.40	$223.40
Purchase #6	$19.78	6.827%	$21.1304	$21.13	$21.15	$21.10
Purchase #7	$69.49	12.571%	$78.2256	$78.23	$78.25	$78.20
7 purchase totals =	$911.36		$976.3407	$976.34	$976.40	$976.40