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	$54.48	5.694%	$57.5821	$57.58	$57.60	$57.60
Purchase #2	$176.76	3.735%	$183.362	$183.36	$183.35	$183.40
Purchase #3	$190.53	11.578%	$212.5896	$212.59	$212.60	$212.60
Purchase #4	$191.43	11.218%	$212.9046	$212.90	$212.90	$212.90
Purchase #5	$100.29	9.363%	$109.6802	$109.68	$109.70	$109.70
Purchase #6	$130.94	7.632%	$140.9333	$140.93	$140.95	$140.90
Purchase #7	$57.91	6.270%	$61.541	$61.54	$61.55	$61.50
7 purchase totals =	$902.34		$978.5928	$978.58	$978.65	$978.60