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	$107.50	3.759%	$111.5409	$111.54	$111.55	$111.50
Purchase #2	$103.78	8.231%	$112.3221	$112.32	$112.30	$112.30
Purchase #3	$35.34	7.475%	$37.9817	$37.98	$38.00	$38.00
Purchase #4	$109.36	3.824%	$113.5419	$113.54	$113.55	$113.50
Purchase #5	$126.84	12.276%	$142.4109	$142.41	$142.40	$142.40
Purchase #6	$145.42	10.872%	$161.2301	$161.23	$161.25	$161.20
Purchase #7	$69.90	5.497%	$73.7424	$73.74	$73.75	$73.70
7 purchase totals =	$698.14		$752.7700	$752.76	$752.80	$752.60