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	$225.59	7.394%	$242.2701	$242.27	$242.25	$242.30
Purchase #2	$44.54	6.553%	$47.4587	$47.46	$47.45	$47.50
Purchase #3	$100.95	6.353%	$107.3634	$107.36	$107.35	$107.40
Purchase #4	$198.88	6.569%	$211.9444	$211.94	$211.95	$211.90
Purchase #5	$85.71	5.461%	$90.3906	$90.39	$90.40	$90.40
Purchase #6	$233.58	4.247%	$243.5001	$243.50	$243.50	$243.50
Purchase #7	$203.28	12.710%	$229.1169	$229.12	$229.10	$229.10
7 purchase totals =	$1,092.53		$1,172.0442	$1,172.04	$1,172.00	$1,172.10