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	$209.86	6.250%	$222.9763	$222.98	$223.00	$223.00
Purchase #2	$222.82	12.142%	$249.8748	$249.87	$249.85	$249.90
Purchase #3	$248.79	12.719%	$280.4336	$280.43	$280.45	$280.40
Purchase #4	$10.38	10.783%	$11.4993	$11.50	$11.50	$11.50
Purchase #5	$143.90	4.453%	$150.3079	$150.31	$150.30	$150.30
Purchase #6	$143.99	4.378%	$150.2939	$150.29	$150.30	$150.30
Purchase #7	$245.39	6.613%	$261.6176	$261.62	$261.60	$261.60
7 purchase totals =	$1,225.13		$1,327.0034	$1,327.00	$1,327.00	$1,327.00