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	$30.71	6.576%	$32.7295	$32.73	$32.75	$32.70
Purchase #2	$48.98	9.146%	$53.4597	$53.46	$53.45	$53.50
Purchase #3	$40.55	7.818%	$43.7202	$43.72	$43.70	$43.70
Purchase #4	$30.66	4.816%	$32.1366	$32.14	$32.15	$32.10
Purchase #5	$184.46	13.611%	$209.5669	$209.57	$209.55	$209.60
Purchase #6	$24.81	13.225%	$28.0911	$28.09	$28.10	$28.10
Purchase #7	$102.27	10.732%	$113.2456	$113.25	$113.25	$113.20
7 purchase totals =	$462.44		$512.9496	$512.96	$512.95	$512.90