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	$127.82	11.706%	$142.7826	$142.78	$142.80	$142.80
Purchase #2	$100.78	10.179%	$111.0384	$111.04	$111.05	$111.00
Purchase #3	$245.40	9.648%	$269.0762	$269.08	$269.10	$269.10
Purchase #4	$57.38	10.107%	$63.1794	$63.18	$63.20	$63.20
Purchase #5	$31.98	7.681%	$34.4364	$34.44	$34.45	$34.40
Purchase #6	$6.98	9.741%	$7.6599	$7.66	$7.65	$7.70
Purchase #7	$90.39	11.180%	$100.4956	$100.50	$100.50	$100.50
7 purchase totals =	$660.73		$728.6685	$728.68	$728.75	$728.70