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	$198.77	12.619%	$223.8528	$223.85	$223.85	$223.90
Purchase #2	$73.56	6.512%	$78.3502	$78.35	$78.35	$78.40
Purchase #3	$14.54	4.126%	$15.1399	$15.14	$15.15	$15.10
Purchase #4	$239.79	8.751%	$260.774	$260.77	$260.75	$260.80
Purchase #5	$98.91	10.574%	$109.3687	$109.37	$109.35	$109.40
Purchase #6	$207.86	7.322%	$223.0795	$223.08	$223.10	$223.10
Purchase #7	$70.39	10.122%	$77.5149	$77.51	$77.50	$77.50
7 purchase totals =	$903.82		$988.0800	$988.07	$988.05	$988.20