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	$52.36	3.321%	$54.0989	$54.10	$54.10	$54.10
Purchase #2	$227.69	9.314%	$248.897	$248.90	$248.90	$248.90
Purchase #3	$80.80	6.605%	$86.1368	$86.14	$86.15	$86.10
Purchase #4	$78.71	6.605%	$83.9088	$83.91	$83.90	$83.90
Purchase #5	$173.40	9.502%	$189.8765	$189.88	$189.90	$189.90
Purchase #6	$89.84	13.412%	$101.8893	$101.89	$101.90	$101.90
Purchase #7	$97.34	3.656%	$100.8988	$100.90	$100.90	$100.90
7 purchase totals =	$800.14		$865.7061	$865.72	$865.75	$865.70