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	$224.39	9.264%	$245.1775	$245.18	$245.20	$245.20
Purchase #2	$174.41	8.383%	$189.0308	$189.03	$189.05	$189.00
Purchase #3	$40.37	13.475%	$45.8099	$45.81	$45.80	$45.80
Purchase #4	$171.98	10.667%	$190.3251	$190.33	$190.35	$190.30
Purchase #5	$10.97	13.424%	$12.4426	$12.44	$12.45	$12.40
Purchase #6	$179.85	4.818%	$188.5152	$188.52	$188.50	$188.50
Purchase #7	$161.27	6.633%	$171.967	$171.97	$171.95	$172.00
7 purchase totals =	$963.24		$1,043.2681	$1,043.28	$1,043.30	$1,043.20