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	$106.96	6.654%	$114.0771	$114.08	$114.10	$114.10
Purchase #2	$127.86	11.404%	$142.4412	$142.44	$142.45	$142.40
Purchase #3	$10.59	9.437%	$11.5894	$11.59	$11.60	$11.60
Purchase #4	$51.89	10.439%	$57.3068	$57.31	$57.30	$57.30
Purchase #5	$197.42	7.646%	$212.5147	$212.51	$212.50	$212.50
Purchase #6	$92.95	6.587%	$99.0726	$99.07	$99.05	$99.10
Purchase #7	$169.59	13.158%	$191.9047	$191.90	$191.90	$191.90
7 purchase totals =	$757.26		$828.9065	$828.90	$828.90	$828.90