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	$103.48	12.525%	$116.4409	$116.44	$116.45	$116.40
Purchase #2	$199.61	11.487%	$222.5392	$222.54	$222.55	$222.50
Purchase #3	$124.39	5.296%	$130.9777	$130.98	$131.00	$131.00
Purchase #4	$171.66	5.179%	$180.5503	$180.55	$180.55	$180.60
Purchase #5	$47.92	6.860%	$51.2073	$51.21	$51.20	$51.20
Purchase #6	$191.77	13.450%	$217.5631	$217.56	$217.55	$217.60
Purchase #7	$236.90	11.717%	$264.6576	$264.66	$264.65	$264.70
7 purchase totals =	$1,075.73		$1,183.9361	$1,183.94	$1,183.95	$1,184.00