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	$249.46	5.642%	$263.5345	$263.53	$263.55	$263.50
Purchase #2	$85.50	13.504%	$97.0459	$97.05	$97.05	$97.00
Purchase #3	$172.84	10.475%	$190.945	$190.95	$190.95	$190.90
Purchase #4	$7.73	9.362%	$8.4537	$8.45	$8.45	$8.50
Purchase #5	$131.88	8.430%	$142.9975	$143.00	$143.00	$143.00
Purchase #6	$59.44	3.771%	$61.6815	$61.68	$61.70	$61.70
Purchase #7	$237.87	5.672%	$251.362	$251.36	$251.35	$251.40
7 purchase totals =	$944.72		$1,016.0201	$1,016.02	$1,016.05	$1,016.00