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	$99.72	10.851%	$110.5406	$110.54	$110.55	$110.50
Purchase #2	$220.89	6.258%	$234.7133	$234.71	$234.70	$234.70
Purchase #3	$71.72	5.385%	$75.5821	$75.58	$75.60	$75.60
Purchase #4	$51.47	7.774%	$55.4713	$55.47	$55.45	$55.50
Purchase #5	$123.25	10.268%	$135.9053	$135.91	$135.90	$135.90
Purchase #6	$192.50	9.784%	$211.3342	$211.33	$211.35	$211.30
Purchase #7	$224.38	5.831%	$237.4636	$237.46	$237.45	$237.50
7 purchase totals =	$983.93		$1,061.0104	$1,061.00	$1,061.00	$1,061.00