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	$201.53	10.473%	$222.6362	$222.64	$222.65	$222.60
Purchase #2	$32.85	7.179%	$35.2083	$35.21	$35.20	$35.20
Purchase #3	$98.32	6.558%	$104.7678	$104.77	$104.75	$104.80
Purchase #4	$134.32	7.314%	$144.1442	$144.14	$144.15	$144.10
Purchase #5	$218.73	12.781%	$246.6859	$246.69	$246.70	$246.70
Purchase #6	$71.76	9.521%	$78.5923	$78.59	$78.60	$78.60
Purchase #7	$107.26	12.155%	$120.2975	$120.30	$120.30	$120.30
7 purchase totals =	$864.77		$952.3322	$952.34	$952.35	$952.30