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	$82.60	8.317%	$89.4698	$89.47	$89.45	$89.50
Purchase #2	$201.69	9.428%	$220.7053	$220.71	$220.70	$220.70
Purchase #3	$195.31	11.438%	$217.6496	$217.65	$217.65	$217.60
Purchase #4	$79.69	12.472%	$89.6289	$89.63	$89.65	$89.60
Purchase #5	$219.54	4.269%	$228.9122	$228.91	$228.90	$228.90
Purchase #6	$183.38	4.321%	$191.3038	$191.30	$191.30	$191.30
Purchase #7	$175.65	6.600%	$187.2429	$187.24	$187.25	$187.20
7 purchase totals =	$1,137.86		$1,224.9125	$1,224.91	$1,224.90	$1,224.80