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	$95.56	8.677%	$103.8517	$103.85	$103.85	$103.90
Purchase #2	$105.82	13.242%	$119.8327	$119.83	$119.85	$119.80
Purchase #3	$32.92	6.553%	$35.0772	$35.08	$35.10	$35.10
Purchase #4	$28.51	13.568%	$32.3782	$32.38	$32.40	$32.40
Purchase #5	$25.52	12.482%	$28.7054	$28.71	$28.70	$28.70
Purchase #6	$189.65	11.540%	$211.5356	$211.54	$211.55	$211.50
Purchase #7	$126.33	10.859%	$140.0482	$140.05	$140.05	$140.00
7 purchase totals =	$604.31		$671.4290	$671.44	$671.50	$671.40