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	$197.86	4.414%	$206.5935	$206.59	$206.60	$206.60
Purchase #2	$22.28	7.423%	$23.9338	$23.93	$23.95	$23.90
Purchase #3	$42.46	7.505%	$45.6466	$45.65	$45.65	$45.60
Purchase #4	$54.74	12.663%	$61.6717	$61.67	$61.65	$61.70
Purchase #5	$182.49	12.607%	$205.4965	$205.50	$205.50	$205.50
Purchase #6	$157.65	8.638%	$171.2678	$171.27	$171.25	$171.30
Purchase #7	$74.66	10.262%	$82.3216	$82.32	$82.30	$82.30
7 purchase totals =	$732.14		$796.9315	$796.93	$796.90	$796.90