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	$104.81	6.774%	$111.9098	$111.91	$111.90	$111.90
Purchase #2	$118.66	6.838%	$126.774	$126.77	$126.75	$126.80
Purchase #3	$59.38	13.364%	$67.3155	$67.32	$67.30	$67.30
Purchase #4	$104.91	12.812%	$118.3511	$118.35	$118.35	$118.40
Purchase #5	$238.48	3.215%	$246.1471	$246.15	$246.15	$246.10
Purchase #6	$101.65	9.795%	$111.6066	$111.61	$111.60	$111.60
Purchase #7	$250.91	5.439%	$264.557	$264.56	$264.55	$264.60
7 purchase totals =	$978.80		$1,046.6611	$1,046.67	$1,046.60	$1,046.70