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	$222.99	7.113%	$238.8513	$238.85	$238.85	$238.90
Purchase #2	$105.46	10.149%	$116.1631	$116.16	$116.15	$116.20
Purchase #3	$194.58	6.364%	$206.9631	$206.96	$206.95	$207.00
Purchase #4	$169.72	10.372%	$187.3234	$187.32	$187.30	$187.30
Purchase #5	$138.76	7.277%	$148.8576	$148.86	$148.85	$148.90
Purchase #6	$234.46	3.403%	$242.4387	$242.44	$242.45	$242.40
Purchase #7	$119.45	6.687%	$127.4376	$127.44	$127.45	$127.40
7 purchase totals =	$1,185.42		$1,268.0348	$1,268.03	$1,268.00	$1,268.10