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	$141.48	10.850%	$156.8306	$156.83	$156.85	$156.80
Purchase #2	$85.86	6.477%	$91.4212	$91.42	$91.40	$91.40
Purchase #3	$170.47	6.670%	$181.8403	$181.84	$181.85	$181.80
Purchase #4	$88.78	3.148%	$91.5748	$91.57	$91.55	$91.60
Purchase #5	$103.58	11.122%	$115.1002	$115.10	$115.10	$115.10
Purchase #6	$38.49	5.287%	$40.525	$40.53	$40.55	$40.50
Purchase #7	$165.89	11.119%	$184.3353	$184.34	$184.35	$184.30
7 purchase totals =	$794.55		$861.6274	$861.63	$861.65	$861.50