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	$161.73	9.122%	$176.483	$176.48	$176.50	$176.50
Purchase #2	$48.35	11.605%	$53.961	$53.96	$53.95	$54.00
Purchase #3	$211.91	6.225%	$225.1014	$225.10	$225.10	$225.10
Purchase #4	$86.43	4.436%	$90.264	$90.26	$90.25	$90.30
Purchase #5	$139.25	9.506%	$152.4871	$152.49	$152.50	$152.50
Purchase #6	$141.84	13.131%	$160.465	$160.47	$160.45	$160.50
Purchase #7	$89.49	13.299%	$101.3913	$101.39	$101.40	$101.40
7 purchase totals =	$879.00		$960.1528	$960.15	$960.15	$960.30