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	$249.97	4.556%	$261.3586	$261.36	$261.35	$261.40
Purchase #2	$195.74	10.289%	$215.8797	$215.88	$215.90	$215.90
Purchase #3	$236.88	4.744%	$248.1176	$248.12	$248.10	$248.10
Purchase #4	$82.39	5.460%	$86.8885	$86.89	$86.90	$86.90
Purchase #5	$242.88	3.601%	$251.6261	$251.63	$251.65	$251.60
Purchase #6	$17.58	12.455%	$19.7696	$19.77	$19.75	$19.80
Purchase #7	$27.29	3.235%	$28.1728	$28.17	$28.15	$28.20
7 purchase totals =	$1,052.73		$1,111.8129	$1,111.82	$1,111.80	$1,111.90