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	$131.95	9.418%	$144.3771	$144.38	$144.40	$144.40
Purchase #2	$112.38	12.846%	$126.8163	$126.82	$126.80	$126.80
Purchase #3	$103.73	5.388%	$109.319	$109.32	$109.30	$109.30
Purchase #4	$17.89	3.584%	$18.5312	$18.53	$18.55	$18.50
Purchase #5	$94.65	6.276%	$100.5902	$100.59	$100.60	$100.60
Purchase #6	$85.63	4.121%	$89.1588	$89.16	$89.15	$89.20
Purchase #7	$101.60	13.704%	$115.5233	$115.52	$115.50	$115.50
7 purchase totals =	$647.83		$704.3159	$704.32	$704.30	$704.30