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	$211.94	5.222%	$223.0075	$223.01	$223.00	$223.00
Purchase #2	$113.88	12.119%	$127.6811	$127.68	$127.70	$127.70
Purchase #3	$33.81	4.660%	$35.3855	$35.39	$35.40	$35.40
Purchase #4	$167.84	8.651%	$182.3598	$182.36	$182.35	$182.40
Purchase #5	$113.34	9.687%	$124.3192	$124.32	$124.30	$124.30
Purchase #6	$122.88	3.767%	$127.5089	$127.51	$127.50	$127.50
Purchase #7	$104.44	10.546%	$115.4542	$115.45	$115.45	$115.50
7 purchase totals =	$868.13		$935.7162	$935.72	$935.70	$935.80