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	$184.88	3.628%	$191.5874	$191.59	$191.60	$191.60
Purchase #2	$213.94	13.292%	$242.3769	$242.38	$242.40	$242.40
Purchase #3	$70.80	11.484%	$78.9307	$78.93	$78.95	$78.90
Purchase #4	$191.67	9.457%	$209.7962	$209.80	$209.80	$209.80
Purchase #5	$241.84	11.402%	$269.4146	$269.41	$269.40	$269.40
Purchase #6	$248.58	4.259%	$259.167	$259.17	$259.15	$259.20
Purchase #7	$67.72	7.137%	$72.5532	$72.55	$72.55	$72.60
7 purchase totals =	$1,219.43		$1,323.8260	$1,323.83	$1,323.85	$1,323.90