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	$216.37	9.817%	$237.611	$237.61	$237.60	$237.60
Purchase #2	$121.27	7.412%	$130.2585	$130.26	$130.25	$130.30
Purchase #3	$197.54	9.284%	$215.8796	$215.88	$215.90	$215.90
Purchase #4	$64.45	10.262%	$71.0639	$71.06	$71.05	$71.10
Purchase #5	$128.91	6.201%	$136.9037	$136.90	$136.90	$136.90
Purchase #6	$245.90	11.250%	$273.5638	$273.56	$273.55	$273.60
Purchase #7	$148.86	6.411%	$158.4034	$158.40	$158.40	$158.40
7 purchase totals =	$1,123.30		$1,223.6839	$1,223.67	$1,223.65	$1,223.80