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	$47.94	10.222%	$52.8404	$52.84	$52.85	$52.80
Purchase #2	$26.90	5.163%	$28.2888	$28.29	$28.30	$28.30
Purchase #3	$110.57	12.520%	$124.4134	$124.41	$124.40	$124.40
Purchase #4	$56.72	10.389%	$62.6126	$62.61	$62.60	$62.60
Purchase #5	$54.82	7.650%	$59.0137	$59.01	$59.00	$59.00
Purchase #6	$69.90	5.607%	$73.8193	$73.82	$73.80	$73.80
Purchase #7	$62.58	9.860%	$68.7504	$68.75	$68.75	$68.80
7 purchase totals =	$429.43		$469.7386	$469.73	$469.70	$469.70