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	$52.61	5.418%	$55.4604	$55.46	$55.45	$55.50
Purchase #2	$224.61	6.582%	$239.3938	$239.39	$239.40	$239.40
Purchase #3	$82.75	3.420%	$85.5801	$85.58	$85.60	$85.60
Purchase #4	$222.66	7.409%	$239.1569	$239.16	$239.15	$239.20
Purchase #5	$222.82	6.868%	$238.1233	$238.12	$238.10	$238.10
Purchase #6	$100.77	4.355%	$105.1585	$105.16	$105.15	$105.20
Purchase #7	$118.56	11.187%	$131.8233	$131.82	$131.80	$131.80
7 purchase totals =	$1,024.78		$1,094.6963	$1,094.69	$1,094.65	$1,094.80