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	$171.51	7.602%	$184.5482	$184.55	$184.55	$184.50
Purchase #2	$249.89	3.438%	$258.4812	$258.48	$258.50	$258.50
Purchase #3	$51.69	3.803%	$53.6558	$53.66	$53.65	$53.70
Purchase #4	$62.65	9.433%	$68.5598	$68.56	$68.55	$68.60
Purchase #5	$25.91	13.584%	$29.4296	$29.43	$29.45	$29.40
Purchase #6	$225.54	13.206%	$255.3248	$255.32	$255.30	$255.30
Purchase #7	$175.31	5.421%	$184.8136	$184.81	$184.80	$184.80
7 purchase totals =	$962.50		$1,034.8130	$1,034.81	$1,034.80	$1,034.80