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	$109.69	4.418%	$114.5361	$114.54	$114.55	$114.50
Purchase #2	$194.35	11.321%	$216.3524	$216.35	$216.35	$216.40
Purchase #3	$101.28	10.670%	$112.0866	$112.09	$112.10	$112.10
Purchase #4	$103.53	5.141%	$108.8525	$108.85	$108.85	$108.90
Purchase #5	$150.85	9.457%	$165.1159	$165.12	$165.10	$165.10
Purchase #6	$181.59	13.146%	$205.4618	$205.46	$205.45	$205.50
Purchase #7	$90.49	3.180%	$93.3676	$93.37	$93.35	$93.40
7 purchase totals =	$931.78		$1,015.7729	$1,015.78	$1,015.75	$1,015.90