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	$207.35	4.316%	$216.2992	$216.30	$216.30	$216.30
Purchase #2	$223.73	8.413%	$242.5524	$242.55	$242.55	$242.60
Purchase #3	$174.84	9.192%	$190.9113	$190.91	$190.90	$190.90
Purchase #4	$140.30	7.314%	$150.5615	$150.56	$150.55	$150.60
Purchase #5	$53.29	8.495%	$57.817	$57.82	$57.80	$57.80
Purchase #6	$50.82	6.252%	$53.9973	$54.00	$54.00	$54.00
Purchase #7	$176.28	6.316%	$187.4138	$187.41	$187.40	$187.40
7 purchase totals =	$1,026.61		$1,099.5525	$1,099.55	$1,099.50	$1,099.60