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	$101.43	7.599%	$109.1377	$109.14	$109.15	$109.10
Purchase #2	$180.87	7.210%	$193.9107	$193.91	$193.90	$193.90
Purchase #3	$220.90	7.808%	$238.1479	$238.15	$238.15	$238.10
Purchase #4	$133.48	7.139%	$143.0091	$143.01	$143.00	$143.00
Purchase #5	$97.73	6.257%	$103.845	$103.85	$103.85	$103.80
Purchase #6	$146.62	13.210%	$165.9885	$165.99	$166.00	$166.00
Purchase #7	$71.35	12.278%	$80.1104	$80.11	$80.10	$80.10
7 purchase totals =	$952.38		$1,034.1493	$1,034.16	$1,034.15	$1,034.00