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	$53.95	13.467%	$61.2154	$61.22	$61.20	$61.20
Purchase #2	$186.29	5.533%	$196.5974	$196.60	$196.60	$196.60
Purchase #3	$41.44	12.643%	$46.6793	$46.68	$46.70	$46.70
Purchase #4	$166.64	11.808%	$186.3169	$186.32	$186.30	$186.30
Purchase #5	$246.59	11.280%	$274.4054	$274.41	$274.40	$274.40
Purchase #6	$14.78	13.145%	$16.7228	$16.72	$16.70	$16.70
Purchase #7	$12.82	12.457%	$14.417	$14.42	$14.40	$14.40
7 purchase totals =	$722.51		$796.3542	$796.37	$796.30	$796.30