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	$183.40	6.777%	$195.829	$195.83	$195.85	$195.80
Purchase #2	$36.96	6.661%	$39.4219	$39.42	$39.40	$39.40
Purchase #3	$152.67	13.214%	$172.8438	$172.84	$172.85	$172.80
Purchase #4	$69.28	6.610%	$73.8594	$73.86	$73.85	$73.90
Purchase #5	$139.73	3.742%	$144.9587	$144.96	$144.95	$145.00
Purchase #6	$89.83	9.646%	$98.495	$98.50	$98.50	$98.50
Purchase #7	$188.82	4.271%	$196.8845	$196.88	$196.90	$196.90
7 purchase totals =	$860.69		$922.2923	$922.29	$922.30	$922.30