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	$175.78	11.562%	$196.1037	$196.10	$196.10	$196.10
Purchase #2	$134.56	4.148%	$140.1415	$140.14	$140.15	$140.10
Purchase #3	$19.57	7.516%	$21.0409	$21.04	$21.05	$21.00
Purchase #4	$106.61	12.365%	$119.7923	$119.79	$119.80	$119.80
Purchase #5	$81.64	9.564%	$89.448	$89.45	$89.45	$89.40
Purchase #6	$215.89	5.406%	$227.561	$227.56	$227.55	$227.60
Purchase #7	$213.57	9.140%	$233.0903	$233.09	$233.10	$233.10
7 purchase totals =	$947.62		$1,027.1777	$1,027.17	$1,027.20	$1,027.10