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	$96.39	3.330%	$99.5998	$99.60	$99.60	$99.60
Purchase #2	$246.37	12.654%	$277.5457	$277.55	$277.55	$277.50
Purchase #3	$45.54	4.330%	$47.5119	$47.51	$47.50	$47.50
Purchase #4	$54.39	9.279%	$59.4368	$59.44	$59.45	$59.40
Purchase #5	$8.80	6.454%	$9.368	$9.37	$9.35	$9.40
Purchase #6	$245.69	4.858%	$257.6256	$257.63	$257.65	$257.60
Purchase #7	$98.99	12.277%	$111.143	$111.14	$111.15	$111.10
7 purchase totals =	$796.17		$862.2308	$862.24	$862.25	$862.10