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	$113.55	12.253%	$127.4633	$127.46	$127.45	$127.50
Purchase #2	$28.33	10.240%	$31.231	$31.23	$31.25	$31.20
Purchase #3	$223.96	13.542%	$254.2887	$254.29	$254.30	$254.30
Purchase #4	$30.56	8.406%	$33.1289	$33.13	$33.15	$33.10
Purchase #5	$170.33	4.397%	$177.8194	$177.82	$177.80	$177.80
Purchase #6	$163.33	4.611%	$170.8611	$170.86	$170.85	$170.90
Purchase #7	$219.88	8.427%	$238.4093	$238.41	$238.40	$238.40
7 purchase totals =	$949.94		$1,033.2017	$1,033.20	$1,033.20	$1,033.20