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	$51.26	6.669%	$54.6785	$54.68	$54.70	$54.70
Purchase #2	$120.99	4.462%	$126.3886	$126.39	$126.40	$126.40
Purchase #3	$82.57	4.355%	$86.1659	$86.17	$86.15	$86.20
Purchase #4	$241.46	6.262%	$256.5802	$256.58	$256.60	$256.60
Purchase #5	$171.89	6.143%	$182.4492	$182.45	$182.45	$182.40
Purchase #6	$200.34	6.757%	$213.877	$213.88	$213.90	$213.90
Purchase #7	$92.76	6.854%	$99.1178	$99.12	$99.10	$99.10
7 purchase totals =	$961.27		$1,019.2572	$1,019.27	$1,019.30	$1,019.30