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	$228.39	9.317%	$249.6691	$249.67	$249.65	$249.70
Purchase #2	$232.91	9.672%	$255.4371	$255.44	$255.45	$255.40
Purchase #3	$159.96	5.402%	$168.601	$168.60	$168.60	$168.60
Purchase #4	$39.78	11.357%	$44.2978	$44.30	$44.30	$44.30
Purchase #5	$55.61	7.256%	$59.6451	$59.65	$59.65	$59.60
Purchase #6	$35.63	10.225%	$39.2732	$39.27	$39.25	$39.30
Purchase #7	$172.54	8.247%	$186.7694	$186.77	$186.75	$186.80
7 purchase totals =	$924.82		$1,003.6927	$1,003.70	$1,003.65	$1,003.70