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	$159.38	9.414%	$174.384	$174.38	$174.40	$174.40
Purchase #2	$179.75	5.504%	$189.6434	$189.64	$189.65	$189.60
Purchase #3	$76.33	3.312%	$78.858	$78.86	$78.85	$78.90
Purchase #4	$37.49	12.258%	$42.0855	$42.09	$42.10	$42.10
Purchase #5	$106.97	11.162%	$118.91	$118.91	$118.90	$118.90
Purchase #6	$46.30	12.755%	$52.2056	$52.21	$52.20	$52.20
Purchase #7	$64.56	6.677%	$68.8707	$68.87	$68.85	$68.90
7 purchase totals =	$670.78		$724.9572	$724.96	$724.95	$725.00