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	$182.69	4.216%	$190.3922	$190.39	$190.40	$190.40
Purchase #2	$104.65	4.764%	$109.6355	$109.64	$109.65	$109.60
Purchase #3	$204.80	9.165%	$223.5699	$223.57	$223.55	$223.60
Purchase #4	$72.54	12.825%	$81.8433	$81.84	$81.85	$81.80
Purchase #5	$152.78	6.652%	$162.9429	$162.94	$162.95	$162.90
Purchase #6	$124.96	9.647%	$137.0149	$137.01	$137.00	$137.00
Purchase #7	$40.75	5.711%	$43.0772	$43.08	$43.10	$43.10
7 purchase totals =	$883.17		$948.4759	$948.47	$948.50	$948.40