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	$168.64	6.235%	$179.1547	$179.15	$179.15	$179.20
Purchase #2	$245.50	9.410%	$268.6016	$268.60	$268.60	$268.60
Purchase #3	$54.95	13.410%	$62.3188	$62.32	$62.30	$62.30
Purchase #4	$198.87	12.103%	$222.9392	$222.94	$222.95	$222.90
Purchase #5	$35.99	11.586%	$40.1598	$40.16	$40.15	$40.20
Purchase #6	$49.57	8.633%	$53.8494	$53.85	$53.85	$53.80
Purchase #7	$199.71	7.703%	$215.0937	$215.09	$215.10	$215.10
7 purchase totals =	$953.23		$1,042.1172	$1,042.11	$1,042.10	$1,042.10