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	$53.76	10.144%	$59.2134	$59.21	$59.20	$59.20
Purchase #2	$93.97	8.382%	$101.8466	$101.85	$101.85	$101.80
Purchase #3	$55.70	6.318%	$59.2191	$59.22	$59.20	$59.20
Purchase #4	$6.59	13.843%	$7.5023	$7.50	$7.50	$7.50
Purchase #5	$28.33	10.613%	$31.3367	$31.34	$31.35	$31.30
Purchase #6	$219.43	13.404%	$248.8424	$248.84	$248.85	$248.80
Purchase #7	$237.57	12.149%	$266.4324	$266.43	$266.45	$266.40
7 purchase totals =	$695.35		$774.3929	$774.39	$774.40	$774.20