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	$250.78	10.110%	$276.1339	$276.13	$276.15	$276.10
Purchase #2	$124.90	6.445%	$132.9498	$132.95	$132.95	$132.90
Purchase #3	$27.72	9.213%	$30.2738	$30.27	$30.25	$30.30
Purchase #4	$135.99	5.111%	$142.9404	$142.94	$142.95	$142.90
Purchase #5	$31.66	13.395%	$35.9009	$35.90	$35.90	$35.90
Purchase #6	$201.81	4.528%	$210.948	$210.95	$210.95	$210.90
Purchase #7	$169.86	11.792%	$189.8899	$189.89	$189.90	$189.90
7 purchase totals =	$942.72		$1,019.0367	$1,019.03	$1,019.05	$1,018.90