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	$45.56	4.230%	$47.4872	$47.49	$47.50	$47.50
Purchase #2	$95.50	10.423%	$105.454	$105.45	$105.45	$105.50
Purchase #3	$199.51	7.127%	$213.7291	$213.73	$213.75	$213.70
Purchase #4	$164.55	12.369%	$184.9032	$184.90	$184.90	$184.90
Purchase #5	$238.71	13.666%	$271.3321	$271.33	$271.35	$271.30
Purchase #6	$171.32	3.539%	$177.383	$177.38	$177.40	$177.40
Purchase #7	$153.59	12.159%	$172.265	$172.27	$172.25	$172.30
7 purchase totals =	$1,068.74		$1,172.5536	$1,172.55	$1,172.60	$1,172.60