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	$112.30	3.131%	$115.8161	$115.82	$115.80	$115.80
Purchase #2	$91.67	13.610%	$104.1463	$104.15	$104.15	$104.10
Purchase #3	$192.67	4.249%	$200.8565	$200.86	$200.85	$200.90
Purchase #4	$116.48	3.370%	$120.4054	$120.41	$120.40	$120.40
Purchase #5	$111.69	5.243%	$117.5459	$117.55	$117.55	$117.50
Purchase #6	$77.66	6.614%	$82.7964	$82.80	$82.80	$82.80
Purchase #7	$70.69	9.537%	$77.4317	$77.43	$77.45	$77.40
7 purchase totals =	$773.16		$818.9983	$819.02	$819.00	$818.90