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	$119.39	10.117%	$131.4687	$131.47	$131.45	$131.50
Purchase #2	$170.55	5.508%	$179.9439	$179.94	$179.95	$179.90
Purchase #3	$21.97	7.209%	$23.5538	$23.55	$23.55	$23.60
Purchase #4	$64.47	10.732%	$71.3889	$71.39	$71.40	$71.40
Purchase #5	$101.35	12.790%	$114.3127	$114.31	$114.30	$114.30
Purchase #6	$216.46	3.275%	$223.5491	$223.55	$223.55	$223.50
Purchase #7	$245.26	4.228%	$255.6296	$255.63	$255.65	$255.60
7 purchase totals =	$939.45		$999.8467	$999.84	$999.85	$999.80