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	$202.50	10.549%	$223.8617	$223.86	$223.85	$223.90
Purchase #2	$71.83	13.452%	$81.4926	$81.49	$81.50	$81.50
Purchase #3	$178.40	11.615%	$199.1212	$199.12	$199.10	$199.10
Purchase #4	$6.49	13.204%	$7.3469	$7.35	$7.35	$7.30
Purchase #5	$196.58	7.496%	$211.3156	$211.32	$211.30	$211.30
Purchase #6	$147.42	13.330%	$167.0711	$167.07	$167.05	$167.10
Purchase #7	$174.71	6.707%	$186.4278	$186.43	$186.45	$186.40
7 purchase totals =	$977.93		$1,076.6369	$1,076.64	$1,076.60	$1,076.60