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	$233.38	13.429%	$264.7206	$264.72	$264.70	$264.70
Purchase #2	$30.78	7.666%	$33.1396	$33.14	$33.15	$33.10
Purchase #3	$194.63	3.827%	$202.0785	$202.08	$202.10	$202.10
Purchase #4	$78.65	13.598%	$89.3448	$89.34	$89.35	$89.30
Purchase #5	$143.84	8.815%	$156.5195	$156.52	$156.50	$156.50
Purchase #6	$90.75	4.718%	$95.0316	$95.03	$95.05	$95.00
Purchase #7	$197.72	8.825%	$215.1688	$215.17	$215.15	$215.20
7 purchase totals =	$969.75		$1,056.0034	$1,056.00	$1,056.00	$1,055.90