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	$177.76	10.394%	$196.2364	$196.24	$196.25	$196.20
Purchase #2	$170.64	5.402%	$179.858	$179.86	$179.85	$179.90
Purchase #3	$55.53	7.211%	$59.5343	$59.53	$59.55	$59.50
Purchase #4	$50.91	3.331%	$52.6058	$52.61	$52.60	$52.60
Purchase #5	$198.55	3.433%	$205.3662	$205.37	$205.35	$205.40
Purchase #6	$90.91	7.601%	$97.8201	$97.82	$97.80	$97.80
Purchase #7	$234.87	9.459%	$257.0864	$257.09	$257.10	$257.10
7 purchase totals =	$979.17		$1,048.5072	$1,048.52	$1,048.50	$1,048.50