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	$159.69	10.609%	$176.6315	$176.63	$176.65	$176.60
Purchase #2	$232.29	11.300%	$258.5388	$258.54	$258.55	$258.50
Purchase #3	$215.61	10.463%	$238.1693	$238.17	$238.15	$238.20
Purchase #4	$96.36	13.691%	$109.5526	$109.55	$109.55	$109.60
Purchase #5	$139.91	9.699%	$153.4799	$153.48	$153.50	$153.50
Purchase #6	$149.51	11.704%	$167.0087	$167.01	$167.00	$167.00
Purchase #7	$205.77	9.774%	$225.882	$225.88	$225.90	$225.90
7 purchase totals =	$1,199.14		$1,329.2628	$1,329.26	$1,329.30	$1,329.30