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	$114.84	13.426%	$130.2584	$130.26	$130.25	$130.30
Purchase #2	$91.83	9.368%	$100.4326	$100.43	$100.45	$100.40
Purchase #3	$203.69	7.710%	$219.3945	$219.39	$219.40	$219.40
Purchase #4	$13.86	7.632%	$14.9178	$14.92	$14.90	$14.90
Purchase #5	$31.58	5.382%	$33.2796	$33.28	$33.30	$33.30
Purchase #6	$140.99	12.623%	$158.7872	$158.79	$158.80	$158.80
Purchase #7	$79.83	8.271%	$86.4327	$86.43	$86.45	$86.40
7 purchase totals =	$676.62		$743.5028	$743.50	$743.55	$743.50