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	$33.46	13.168%	$37.866	$37.87	$37.85	$37.90
Purchase #2	$63.97	5.357%	$67.3969	$67.40	$67.40	$67.40
Purchase #3	$91.52	12.843%	$103.2739	$103.27	$103.25	$103.30
Purchase #4	$221.55	9.572%	$242.7568	$242.76	$242.75	$242.80
Purchase #5	$246.70	3.596%	$255.5713	$255.57	$255.55	$255.60
Purchase #6	$119.83	5.765%	$126.7382	$126.74	$126.75	$126.70
Purchase #7	$196.99	13.577%	$223.7353	$223.74	$223.75	$223.70
7 purchase totals =	$974.02		$1,057.3384	$1,057.35	$1,057.30	$1,057.40