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	$97.96	7.664%	$105.4677	$105.47	$105.45	$105.50
Purchase #2	$167.47	10.750%	$185.473	$185.47	$185.45	$185.50
Purchase #3	$175.28	8.537%	$190.2437	$190.24	$190.25	$190.20
Purchase #4	$223.94	3.527%	$231.8384	$231.84	$231.85	$231.80
Purchase #5	$29.97	13.231%	$33.9353	$33.94	$33.95	$33.90
Purchase #6	$186.80	9.786%	$205.0802	$205.08	$205.10	$205.10
Purchase #7	$128.97	8.431%	$139.8435	$139.84	$139.85	$139.80
7 purchase totals =	$1,010.39		$1,091.8818	$1,091.88	$1,091.90	$1,091.80