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	$145.70	6.871%	$155.711	$155.71	$155.70	$155.70
Purchase #2	$170.33	10.857%	$188.8227	$188.82	$188.80	$188.80
Purchase #3	$87.61	4.200%	$91.2896	$91.29	$91.30	$91.30
Purchase #4	$131.59	12.420%	$147.9335	$147.93	$147.95	$147.90
Purchase #5	$117.32	7.417%	$126.0216	$126.02	$126.00	$126.00
Purchase #6	$134.40	3.806%	$139.5153	$139.52	$139.50	$139.50
Purchase #7	$191.51	4.293%	$199.7315	$199.73	$199.75	$199.70
7 purchase totals =	$978.46		$1,049.0252	$1,049.02	$1,049.00	$1,048.90