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	$197.56	13.335%	$223.9046	$223.90	$223.90	$223.90
Purchase #2	$108.58	9.688%	$119.0992	$119.10	$119.10	$119.10
Purchase #3	$99.68	10.287%	$109.9341	$109.93	$109.95	$109.90
Purchase #4	$202.96	9.564%	$222.3711	$222.37	$222.35	$222.40
Purchase #5	$168.30	10.238%	$185.5306	$185.53	$185.55	$185.50
Purchase #6	$205.87	11.604%	$229.7592	$229.76	$229.75	$229.80
Purchase #7	$5.95	5.597%	$6.283	$6.28	$6.30	$6.30
7 purchase totals =	$988.90		$1,096.8818	$1,096.87	$1,096.90	$1,096.90