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	$169.58	7.778%	$182.7699	$182.77	$182.75	$182.80
Purchase #2	$153.72	6.700%	$164.0192	$164.02	$164.00	$164.00
Purchase #3	$42.55	13.207%	$48.1696	$48.17	$48.15	$48.20
Purchase #4	$72.88	12.210%	$81.7786	$81.78	$81.80	$81.80
Purchase #5	$234.89	12.503%	$264.2583	$264.26	$264.25	$264.30
Purchase #6	$178.38	10.371%	$196.8798	$196.88	$196.90	$196.90
Purchase #7	$142.92	11.342%	$159.13	$159.13	$159.15	$159.10
7 purchase totals =	$994.92		$1,097.0054	$1,097.01	$1,097.00	$1,097.10