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	$134.89	3.824%	$140.0482	$140.05	$140.05	$140.00
Purchase #2	$158.54	3.613%	$164.2681	$164.27	$164.25	$164.30
Purchase #3	$163.86	3.470%	$169.5459	$169.55	$169.55	$169.50
Purchase #4	$100.84	5.864%	$106.7533	$106.75	$106.75	$106.80
Purchase #5	$68.55	7.629%	$73.7797	$73.78	$73.80	$73.80
Purchase #6	$73.46	12.704%	$82.7924	$82.79	$82.80	$82.80
Purchase #7	$154.64	11.435%	$172.3231	$172.32	$172.30	$172.30
7 purchase totals =	$854.78		$909.5107	$909.51	$909.50	$909.50