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	$111.82	5.131%	$117.5575	$117.56	$117.55	$117.60
Purchase #2	$196.85	9.302%	$215.161	$215.16	$215.15	$215.20
Purchase #3	$188.85	9.821%	$207.397	$207.40	$207.40	$207.40
Purchase #4	$223.63	11.123%	$248.5044	$248.50	$248.50	$248.50
Purchase #5	$191.46	12.740%	$215.852	$215.85	$215.85	$215.90
Purchase #6	$45.25	10.683%	$50.0841	$50.08	$50.10	$50.10
Purchase #7	$143.96	11.557%	$160.5975	$160.60	$160.60	$160.60
7 purchase totals =	$1,101.82		$1,215.1535	$1,215.15	$1,215.15	$1,215.30