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	$209.31	3.346%	$216.3135	$216.31	$216.30	$216.30
Purchase #2	$240.65	10.697%	$266.3923	$266.39	$266.40	$266.40
Purchase #3	$137.42	7.284%	$147.4297	$147.43	$147.45	$147.40
Purchase #4	$138.28	8.749%	$150.3781	$150.38	$150.40	$150.40
Purchase #5	$167.66	3.535%	$173.5868	$173.59	$173.60	$173.60
Purchase #6	$52.99	12.401%	$59.5613	$59.56	$59.55	$59.60
Purchase #7	$98.26	6.492%	$104.639	$104.64	$104.65	$104.60
7 purchase totals =	$1,044.57		$1,118.3007	$1,118.30	$1,118.35	$1,118.30