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	$38.93	6.716%	$41.5445	$41.54	$41.55	$41.50
Purchase #2	$190.50	4.111%	$198.3315	$198.33	$198.35	$198.30
Purchase #3	$224.64	5.404%	$236.7795	$236.78	$236.80	$236.80
Purchase #4	$58.98	9.400%	$64.5241	$64.52	$64.50	$64.50
Purchase #5	$220.80	12.466%	$248.3249	$248.32	$248.30	$248.30
Purchase #6	$49.33	11.469%	$54.9877	$54.99	$55.00	$55.00
Purchase #7	$83.65	6.512%	$89.0973	$89.10	$89.10	$89.10
7 purchase totals =	$866.83		$933.5895	$933.58	$933.60	$933.50