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	$50.58	7.443%	$54.3447	$54.34	$54.35	$54.30
Purchase #2	$238.51	6.424%	$253.8319	$253.83	$253.85	$253.80
Purchase #3	$139.82	7.520%	$150.3345	$150.33	$150.35	$150.30
Purchase #4	$158.82	5.476%	$167.517	$167.52	$167.50	$167.50
Purchase #5	$57.47	12.653%	$64.7417	$64.74	$64.75	$64.70
Purchase #6	$150.92	9.868%	$165.8128	$165.81	$165.80	$165.80
Purchase #7	$196.41	4.684%	$205.6098	$205.61	$205.60	$205.60
7 purchase totals =	$992.53		$1,062.1924	$1,062.18	$1,062.20	$1,062.00