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	$56.42	10.839%	$62.5354	$62.54	$62.55	$62.50
Purchase #2	$99.26	10.772%	$109.9523	$109.95	$109.95	$110.00
Purchase #3	$152.96	13.784%	$174.044	$174.04	$174.05	$174.00
Purchase #4	$248.50	12.666%	$279.975	$279.98	$280.00	$280.00
Purchase #5	$232.85	7.835%	$251.0938	$251.09	$251.10	$251.10
Purchase #6	$216.27	10.303%	$238.5523	$238.55	$238.55	$238.60
Purchase #7	$229.26	9.228%	$250.4161	$250.42	$250.40	$250.40
7 purchase totals =	$1,235.52		$1,366.5689	$1,366.57	$1,366.60	$1,366.60