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	$162.63	12.335%	$182.6904	$182.69	$182.70	$182.70
Purchase #2	$80.60	7.360%	$86.5322	$86.53	$86.55	$86.50
Purchase #3	$65.61	8.553%	$71.2216	$71.22	$71.20	$71.20
Purchase #4	$193.65	3.320%	$200.0792	$200.08	$200.10	$200.10
Purchase #5	$236.78	7.727%	$255.076	$255.08	$255.10	$255.10
Purchase #6	$89.71	10.145%	$98.8111	$98.81	$98.80	$98.80
Purchase #7	$19.53	7.761%	$21.0457	$21.05	$21.05	$21.00
7 purchase totals =	$848.51		$915.4562	$915.46	$915.50	$915.40