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	$240.89	5.173%	$253.3512	$253.35	$253.35	$253.40
Purchase #2	$118.35	11.859%	$132.3851	$132.39	$132.40	$132.40
Purchase #3	$98.93	5.389%	$104.2613	$104.26	$104.25	$104.30
Purchase #4	$142.85	13.691%	$162.4076	$162.41	$162.40	$162.40
Purchase #5	$186.43	7.306%	$200.0506	$200.05	$200.05	$200.10
Purchase #6	$64.39	13.466%	$73.0608	$73.06	$73.05	$73.10
Purchase #7	$77.54	6.689%	$82.7267	$82.73	$82.75	$82.70
7 purchase totals =	$929.38		$1,008.2433	$1,008.25	$1,008.25	$1,008.40