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	$132.89	11.475%	$148.1391	$148.14	$148.15	$148.10
Purchase #2	$211.31	13.550%	$239.9425	$239.94	$239.95	$239.90
Purchase #3	$200.42	11.284%	$223.0354	$223.04	$223.05	$223.00
Purchase #4	$121.65	12.113%	$136.3855	$136.39	$136.40	$136.40
Purchase #5	$78.76	4.444%	$82.2601	$82.26	$82.25	$82.30
Purchase #6	$215.61	11.802%	$241.0563	$241.06	$241.05	$241.10
Purchase #7	$171.67	7.774%	$185.0156	$185.02	$185.00	$185.00
7 purchase totals =	$1,132.31		$1,255.8345	$1,255.85	$1,255.85	$1,255.80