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	$38.48	7.562%	$41.3899	$41.39	$41.40	$41.40
Purchase #2	$220.74	11.313%	$245.7123	$245.71	$245.70	$245.70
Purchase #3	$89.37	12.220%	$100.291	$100.29	$100.30	$100.30
Purchase #4	$190.82	4.149%	$198.7371	$198.74	$198.75	$198.70
Purchase #5	$101.49	7.336%	$108.9353	$108.94	$108.95	$108.90
Purchase #6	$37.93	11.488%	$42.2874	$42.29	$42.30	$42.30
Purchase #7	$128.61	11.190%	$143.0015	$143.00	$143.00	$143.00
7 purchase totals =	$807.44		$880.3545	$880.36	$880.40	$880.30