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	$7.32	7.579%	$7.8748	$7.87	$7.85	$7.90
Purchase #2	$181.50	5.244%	$191.0179	$191.02	$191.00	$191.00
Purchase #3	$84.71	7.242%	$90.8447	$90.84	$90.85	$90.80
Purchase #4	$217.57	6.683%	$232.1102	$232.11	$232.10	$232.10
Purchase #5	$191.96	12.115%	$215.216	$215.22	$215.20	$215.20
Purchase #6	$247.54	3.330%	$255.7831	$255.78	$255.80	$255.80
Purchase #7	$30.49	7.441%	$32.7588	$32.76	$32.75	$32.80
7 purchase totals =	$961.09		$1,025.6055	$1,025.60	$1,025.55	$1,025.60