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	$85.30	13.170%	$96.534	$96.53	$96.55	$96.50
Purchase #2	$246.61	3.396%	$254.9849	$254.98	$255.00	$255.00
Purchase #3	$64.98	12.511%	$73.1096	$73.11	$73.10	$73.10
Purchase #4	$47.58	5.203%	$50.0556	$50.06	$50.05	$50.10
Purchase #5	$156.92	3.489%	$162.3949	$162.39	$162.40	$162.40
Purchase #6	$162.31	10.621%	$179.5489	$179.55	$179.55	$179.50
Purchase #7	$248.78	12.796%	$280.6139	$280.61	$280.60	$280.60
7 purchase totals =	$1,012.48		$1,097.2418	$1,097.23	$1,097.25	$1,097.20