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	$103.62	7.518%	$111.4102	$111.41	$111.40	$111.40
Purchase #2	$151.61	7.167%	$162.4759	$162.48	$162.50	$162.50
Purchase #3	$210.35	5.848%	$222.6513	$222.65	$222.65	$222.70
Purchase #4	$92.44	6.674%	$98.6094	$98.61	$98.60	$98.60
Purchase #5	$49.43	4.169%	$51.4907	$51.49	$51.50	$51.50
Purchase #6	$109.90	8.758%	$119.525	$119.53	$119.55	$119.50
Purchase #7	$209.91	5.639%	$221.7468	$221.75	$221.75	$221.70
7 purchase totals =	$927.26		$987.9093	$987.92	$987.95	$987.90