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	$186.83	5.117%	$196.3901	$196.39	$196.40	$196.40
Purchase #2	$226.96	6.305%	$241.2698	$241.27	$241.25	$241.30
Purchase #3	$52.66	9.727%	$57.7822	$57.78	$57.80	$57.80
Purchase #4	$82.73	12.427%	$93.0109	$93.01	$93.00	$93.00
Purchase #5	$244.44	8.279%	$264.6772	$264.68	$264.70	$264.70
Purchase #6	$177.79	12.275%	$199.6137	$199.61	$199.60	$199.60
Purchase #7	$211.96	5.104%	$222.7784	$222.78	$222.80	$222.80
7 purchase totals =	$1,183.37		$1,275.5223	$1,275.52	$1,275.55	$1,275.60