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	$186.39	9.679%	$204.4307	$204.43	$204.45	$204.40
Purchase #2	$66.48	13.172%	$75.2367	$75.24	$75.25	$75.20
Purchase #3	$35.50	11.280%	$39.5044	$39.50	$39.50	$39.50
Purchase #4	$82.97	8.292%	$89.8499	$89.85	$89.85	$89.80
Purchase #5	$198.55	9.439%	$217.2911	$217.29	$217.30	$217.30
Purchase #6	$180.51	6.767%	$192.7251	$192.73	$192.75	$192.70
Purchase #7	$190.73	3.513%	$197.4303	$197.43	$197.45	$197.40
7 purchase totals =	$941.13		$1,016.4682	$1,016.47	$1,016.55	$1,016.30