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	$70.93	5.504%	$74.834	$74.83	$74.85	$74.80
Purchase #2	$168.44	3.586%	$174.4803	$174.48	$174.50	$174.50
Purchase #3	$161.84	4.406%	$168.9707	$168.97	$168.95	$169.00
Purchase #4	$99.29	10.612%	$109.8267	$109.83	$109.85	$109.80
Purchase #5	$154.82	6.791%	$165.3338	$165.33	$165.35	$165.30
Purchase #6	$184.93	6.392%	$196.7507	$196.75	$196.75	$196.80
Purchase #7	$93.30	12.416%	$104.8841	$104.88	$104.90	$104.90
7 purchase totals =	$933.55		$995.0803	$995.07	$995.15	$995.10