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	$110.94	13.330%	$125.7283	$125.73	$125.75	$125.70
Purchase #2	$101.41	10.127%	$111.6798	$111.68	$111.70	$111.70
Purchase #3	$121.38	8.350%	$131.5152	$131.52	$131.50	$131.50
Purchase #4	$138.86	8.314%	$150.4048	$150.40	$150.40	$150.40
Purchase #5	$97.31	6.274%	$103.4152	$103.42	$103.40	$103.40
Purchase #6	$57.72	6.367%	$61.395	$61.40	$61.40	$61.40
Purchase #7	$71.47	3.403%	$73.9021	$73.90	$73.90	$73.90
7 purchase totals =	$699.09		$758.0404	$758.05	$758.05	$758.00