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	$168.59	10.140%	$185.685	$185.69	$185.70	$185.70
Purchase #2	$79.54	4.736%	$83.307	$83.31	$83.30	$83.30
Purchase #3	$186.71	11.406%	$208.0061	$208.01	$208.00	$208.00
Purchase #4	$51.85	6.817%	$55.3846	$55.38	$55.40	$55.40
Purchase #5	$25.35	13.559%	$28.7872	$28.79	$28.80	$28.80
Purchase #6	$192.34	6.532%	$204.9036	$204.90	$204.90	$204.90
Purchase #7	$86.59	9.526%	$94.8386	$94.84	$94.85	$94.80
7 purchase totals =	$790.97		$860.9121	$860.92	$860.95	$860.90