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	$68.46	10.836%	$75.8783	$75.88	$75.90	$75.90
Purchase #2	$38.97	8.531%	$42.2945	$42.29	$42.30	$42.30
Purchase #3	$47.88	5.389%	$50.4603	$50.46	$50.45	$50.50
Purchase #4	$198.96	5.237%	$209.3795	$209.38	$209.40	$209.40
Purchase #5	$63.33	6.627%	$67.5269	$67.53	$67.55	$67.50
Purchase #6	$129.59	10.274%	$142.9041	$142.90	$142.90	$142.90
Purchase #7	$60.79	3.200%	$62.7353	$62.74	$62.75	$62.70
7 purchase totals =	$607.98		$651.1789	$651.18	$651.25	$651.20