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	$232.86	4.112%	$242.4352	$242.44	$242.45	$242.40
Purchase #2	$158.32	4.117%	$164.838	$164.84	$164.85	$164.80
Purchase #3	$79.26	4.498%	$82.8251	$82.83	$82.85	$82.80
Purchase #4	$119.64	3.284%	$123.569	$123.57	$123.55	$123.60
Purchase #5	$102.83	6.766%	$109.7875	$109.79	$109.80	$109.80
Purchase #6	$238.30	12.534%	$268.1685	$268.17	$268.15	$268.20
Purchase #7	$20.79	11.654%	$23.2129	$23.21	$23.20	$23.20
7 purchase totals =	$952.00		$1,014.8362	$1,014.85	$1,014.85	$1,014.80