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	$64.56	7.335%	$69.2955	$69.30	$69.30	$69.30
Purchase #2	$72.39	13.577%	$82.2184	$82.22	$82.20	$82.20
Purchase #3	$215.29	11.109%	$239.2066	$239.21	$239.20	$239.20
Purchase #4	$176.54	11.240%	$196.3831	$196.38	$196.40	$196.40
Purchase #5	$78.47	9.158%	$85.6563	$85.66	$85.65	$85.70
Purchase #6	$249.39	6.181%	$264.8048	$264.80	$264.80	$264.80
Purchase #7	$128.50	11.448%	$143.2107	$143.21	$143.20	$143.20
7 purchase totals =	$985.14		$1,080.7754	$1,080.78	$1,080.75	$1,080.80