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	$212.88	3.616%	$220.5777	$220.58	$220.60	$220.60
Purchase #2	$188.63	4.351%	$196.8373	$196.84	$196.85	$196.80
Purchase #3	$70.88	10.588%	$78.3848	$78.38	$78.40	$78.40
Purchase #4	$250.39	13.746%	$284.8086	$284.81	$284.80	$284.80
Purchase #5	$229.52	11.308%	$255.4741	$255.47	$255.45	$255.50
Purchase #6	$22.38	12.375%	$25.1495	$25.15	$25.15	$25.10
Purchase #7	$54.57	8.346%	$59.1244	$59.12	$59.10	$59.10
7 purchase totals =	$1,029.25		$1,120.3564	$1,120.35	$1,120.35	$1,120.30