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	$202.71	7.787%	$218.495	$218.50	$218.50	$218.50
Purchase #2	$186.72	5.130%	$196.2987	$196.30	$196.30	$196.30
Purchase #3	$245.28	11.523%	$273.5436	$273.54	$273.55	$273.50
Purchase #4	$79.29	8.365%	$85.9226	$85.92	$85.90	$85.90
Purchase #5	$223.90	9.153%	$244.3936	$244.39	$244.40	$244.40
Purchase #6	$222.69	8.510%	$241.6409	$241.64	$241.65	$241.60
Purchase #7	$149.63	12.556%	$168.4175	$168.42	$168.40	$168.40
7 purchase totals =	$1,310.22		$1,428.7119	$1,428.71	$1,428.70	$1,428.60