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	$117.38	7.759%	$126.4875	$126.49	$126.50	$126.50
Purchase #2	$215.86	8.377%	$233.9426	$233.94	$233.95	$233.90
Purchase #3	$78.70	13.435%	$89.2733	$89.27	$89.25	$89.30
Purchase #4	$166.79	3.367%	$172.4058	$172.41	$172.40	$172.40
Purchase #5	$246.26	13.524%	$279.5642	$279.56	$279.55	$279.60
Purchase #6	$55.43	4.415%	$57.8772	$57.88	$57.90	$57.90
Purchase #7	$70.71	8.774%	$76.9141	$76.91	$76.90	$76.90
7 purchase totals =	$951.13		$1,036.4647	$1,036.46	$1,036.45	$1,036.50