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	$200.90	10.703%	$222.4023	$222.40	$222.40	$222.40
Purchase #2	$112.27	10.206%	$123.7283	$123.73	$123.75	$123.70
Purchase #3	$12.33	6.163%	$13.0899	$13.09	$13.10	$13.10
Purchase #4	$239.64	12.450%	$269.4752	$269.48	$269.50	$269.50
Purchase #5	$166.55	7.773%	$179.4959	$179.50	$179.50	$179.50
Purchase #6	$149.34	11.416%	$166.3887	$166.39	$166.40	$166.40
Purchase #7	$79.62	3.694%	$82.5612	$82.56	$82.55	$82.60
7 purchase totals =	$960.65		$1,057.1415	$1,057.15	$1,057.20	$1,057.20