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	$201.53	5.614%	$212.8439	$212.84	$212.85	$212.80
Purchase #2	$91.37	5.430%	$96.3314	$96.33	$96.35	$96.30
Purchase #3	$123.87	6.346%	$131.7308	$131.73	$131.75	$131.70
Purchase #4	$187.73	4.808%	$196.7561	$196.76	$196.75	$196.80
Purchase #5	$53.39	13.256%	$60.4674	$60.47	$60.45	$60.50
Purchase #6	$130.80	7.122%	$140.1156	$140.12	$140.10	$140.10
Purchase #7	$42.52	11.171%	$47.2699	$47.27	$47.25	$47.30
7 purchase totals =	$831.21		$885.5151	$885.52	$885.50	$885.50