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	$144.72	13.836%	$164.7435	$164.74	$164.75	$164.70
Purchase #2	$61.35	12.615%	$69.0893	$69.09	$69.10	$69.10
Purchase #3	$157.32	11.133%	$174.8344	$174.83	$174.85	$174.80
Purchase #4	$188.49	13.280%	$213.5215	$213.52	$213.50	$213.50
Purchase #5	$156.87	5.507%	$165.5088	$165.51	$165.50	$165.50
Purchase #6	$146.47	7.396%	$157.3029	$157.30	$157.30	$157.30
Purchase #7	$131.26	6.573%	$139.8877	$139.89	$139.90	$139.90
7 purchase totals =	$986.48		$1,084.8881	$1,084.88	$1,084.90	$1,084.80