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	$246.65	6.741%	$263.2767	$263.28	$263.30	$263.30
Purchase #2	$76.40	12.831%	$86.2029	$86.20	$86.20	$86.20
Purchase #3	$130.80	5.312%	$137.7481	$137.75	$137.75	$137.70
Purchase #4	$166.50	9.364%	$182.0911	$182.09	$182.10	$182.10
Purchase #5	$129.87	10.148%	$143.0492	$143.05	$143.05	$143.00
Purchase #6	$121.34	4.758%	$127.1134	$127.11	$127.10	$127.10
Purchase #7	$99.28	12.387%	$111.5778	$111.58	$111.60	$111.60
7 purchase totals =	$970.84		$1,051.0592	$1,051.06	$1,051.10	$1,051.00