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	$185.35	13.696%	$210.7355	$210.74	$210.75	$210.70
Purchase #2	$183.91	13.545%	$208.8206	$208.82	$208.80	$208.80
Purchase #3	$123.33	5.745%	$130.4153	$130.42	$130.40	$130.40
Purchase #4	$62.83	6.476%	$66.8989	$66.90	$66.90	$66.90
Purchase #5	$224.40	7.684%	$241.6429	$241.64	$241.65	$241.60
Purchase #6	$85.46	12.626%	$96.2502	$96.25	$96.25	$96.30
Purchase #7	$57.43	8.715%	$62.435	$62.44	$62.45	$62.40
7 purchase totals =	$922.71		$1,017.1984	$1,017.21	$1,017.20	$1,017.10