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	$30.85	5.451%	$32.5316	$32.53	$32.55	$32.50
Purchase #2	$98.31	6.411%	$104.6127	$104.61	$104.60	$104.60
Purchase #3	$187.84	4.534%	$196.3567	$196.36	$196.35	$196.40
Purchase #4	$192.27	3.809%	$199.5936	$199.59	$199.60	$199.60
Purchase #5	$241.87	3.407%	$250.1105	$250.11	$250.10	$250.10
Purchase #6	$242.46	7.831%	$261.447	$261.45	$261.45	$261.40
Purchase #7	$175.76	13.418%	$199.3435	$199.34	$199.35	$199.30
7 purchase totals =	$1,169.36		$1,243.9956	$1,243.99	$1,244.00	$1,243.90