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	$77.75	9.234%	$84.9294	$84.93	$84.95	$84.90
Purchase #2	$195.75	4.642%	$204.8367	$204.84	$204.85	$204.80
Purchase #3	$98.75	10.527%	$109.1454	$109.15	$109.15	$109.10
Purchase #4	$249.76	9.464%	$273.3973	$273.40	$273.40	$273.40
Purchase #5	$74.89	4.228%	$78.0563	$78.06	$78.05	$78.10
Purchase #6	$202.58	6.559%	$215.8672	$215.87	$215.85	$215.90
Purchase #7	$91.60	4.202%	$95.449	$95.45	$95.45	$95.40
7 purchase totals =	$991.08		$1,061.6813	$1,061.70	$1,061.70	$1,061.60