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	$65.25	8.149%	$70.5672	$70.57	$70.55	$70.60
Purchase #2	$160.78	3.647%	$166.6436	$166.64	$166.65	$166.60
Purchase #3	$181.38	9.696%	$198.9666	$198.97	$198.95	$199.00
Purchase #4	$154.78	7.179%	$165.8917	$165.89	$165.90	$165.90
Purchase #5	$48.83	13.756%	$55.5471	$55.55	$55.55	$55.50
Purchase #6	$53.77	10.315%	$59.3164	$59.32	$59.30	$59.30
Purchase #7	$242.54	3.305%	$250.5559	$250.56	$250.55	$250.60
7 purchase totals =	$907.33		$967.4885	$967.50	$967.45	$967.50