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	$209.29	9.173%	$228.4882	$228.49	$228.50	$228.50
Purchase #2	$144.74	13.843%	$164.7764	$164.78	$164.80	$164.80
Purchase #3	$130.26	9.802%	$143.0281	$143.03	$143.05	$143.00
Purchase #4	$10.32	9.735%	$11.3247	$11.32	$11.30	$11.30
Purchase #5	$173.93	9.371%	$190.229	$190.23	$190.25	$190.20
Purchase #6	$172.66	5.863%	$182.7831	$182.78	$182.80	$182.80
Purchase #7	$173.95	9.850%	$191.0841	$191.08	$191.10	$191.10
7 purchase totals =	$1,015.15		$1,111.7136	$1,111.71	$1,111.80	$1,111.70