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	$149.60	4.798%	$156.7778	$156.78	$156.80	$156.80
Purchase #2	$45.85	6.199%	$48.6922	$48.69	$48.70	$48.70
Purchase #3	$236.93	3.535%	$245.3055	$245.31	$245.30	$245.30
Purchase #4	$71.69	7.209%	$76.8581	$76.86	$76.85	$76.90
Purchase #5	$93.41	10.779%	$103.4787	$103.48	$103.50	$103.50
Purchase #6	$200.96	5.220%	$211.4501	$211.45	$211.45	$211.50
Purchase #7	$230.69	4.795%	$241.7516	$241.75	$241.75	$241.80
7 purchase totals =	$1,029.13		$1,084.3140	$1,084.32	$1,084.35	$1,084.50