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	$103.95	5.732%	$109.9084	$109.91	$109.90	$109.90
Purchase #2	$212.40	11.644%	$237.1319	$237.13	$237.15	$237.10
Purchase #3	$237.88	7.398%	$255.4784	$255.48	$255.50	$255.50
Purchase #4	$63.50	11.517%	$70.8133	$70.81	$70.80	$70.80
Purchase #5	$48.71	5.670%	$51.4719	$51.47	$51.45	$51.50
Purchase #6	$208.58	7.291%	$223.7876	$223.79	$223.80	$223.80
Purchase #7	$213.31	9.813%	$234.2421	$234.24	$234.25	$234.20
7 purchase totals =	$1,088.33		$1,182.8336	$1,182.83	$1,182.85	$1,182.80