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	$117.46	5.367%	$123.7641	$123.76	$123.75	$123.80
Purchase #2	$161.62	8.191%	$174.8583	$174.86	$174.85	$174.90
Purchase #3	$249.95	4.776%	$261.8876	$261.89	$261.90	$261.90
Purchase #4	$63.85	13.731%	$72.6172	$72.62	$72.60	$72.60
Purchase #5	$185.88	9.820%	$204.1334	$204.13	$204.15	$204.10
Purchase #6	$233.31	12.537%	$262.5601	$262.56	$262.55	$262.60
Purchase #7	$107.47	10.814%	$119.0918	$119.09	$119.10	$119.10
7 purchase totals =	$1,119.54		$1,218.9125	$1,218.91	$1,218.90	$1,219.00