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	$28.54	12.599%	$32.1358	$32.14	$32.15	$32.10
Purchase #2	$6.26	4.183%	$6.5219	$6.52	$6.50	$6.50
Purchase #3	$15.73	3.446%	$16.2721	$16.27	$16.25	$16.30
Purchase #4	$206.65	5.803%	$218.6419	$218.64	$218.65	$218.60
Purchase #5	$73.64	9.293%	$80.4834	$80.48	$80.50	$80.50
Purchase #6	$118.61	7.357%	$127.3361	$127.34	$127.35	$127.30
Purchase #7	$158.87	8.672%	$172.6472	$172.65	$172.65	$172.60
7 purchase totals =	$608.30		$654.0384	$654.04	$654.05	$653.90