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	$249.43	6.391%	$265.3711	$265.37	$265.35	$265.40
Purchase #2	$181.78	4.670%	$190.2691	$190.27	$190.25	$190.30
Purchase #3	$125.79	4.405%	$131.331	$131.33	$131.35	$131.30
Purchase #4	$241.40	4.108%	$251.3167	$251.32	$251.30	$251.30
Purchase #5	$47.82	11.829%	$53.4766	$53.48	$53.50	$53.50
Purchase #6	$131.66	4.276%	$137.2898	$137.29	$137.30	$137.30
Purchase #7	$174.57	4.222%	$181.9403	$181.94	$181.95	$181.90
7 purchase totals =	$1,152.45		$1,210.9946	$1,211.00	$1,211.00	$1,211.00