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	$83.72	3.801%	$86.9022	$86.90	$86.90	$86.90
Purchase #2	$193.35	3.692%	$200.4885	$200.49	$200.50	$200.50
Purchase #3	$193.99	10.869%	$215.0748	$215.07	$215.05	$215.10
Purchase #4	$31.49	6.268%	$33.4638	$33.46	$33.45	$33.50
Purchase #5	$190.59	11.603%	$212.7042	$212.70	$212.70	$212.70
Purchase #6	$213.27	5.702%	$225.4307	$225.43	$225.45	$225.40
Purchase #7	$59.78	4.159%	$62.2663	$62.27	$62.25	$62.30
7 purchase totals =	$966.19		$1,036.3305	$1,036.32	$1,036.30	$1,036.40