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	$92.85	9.363%	$101.5435	$101.54	$101.55	$101.50
Purchase #2	$190.65	9.470%	$208.7046	$208.70	$208.70	$208.70
Purchase #3	$100.30	9.267%	$109.5948	$109.59	$109.60	$109.60
Purchase #4	$245.76	9.708%	$269.6184	$269.62	$269.60	$269.60
Purchase #5	$53.68	11.701%	$59.9611	$59.96	$59.95	$60.00
Purchase #6	$130.42	4.577%	$136.3893	$136.39	$136.40	$136.40
Purchase #7	$164.53	4.284%	$171.5785	$171.58	$171.60	$171.60
7 purchase totals =	$978.19		$1,057.3902	$1,057.38	$1,057.40	$1,057.40