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	$159.59	10.560%	$176.4427	$176.44	$176.45	$176.40
Purchase #2	$53.90	13.239%	$61.0358	$61.04	$61.05	$61.00
Purchase #3	$89.93	11.480%	$100.254	$100.25	$100.25	$100.30
Purchase #4	$244.48	8.348%	$264.8892	$264.89	$264.90	$264.90
Purchase #5	$98.96	7.630%	$106.5106	$106.51	$106.50	$106.50
Purchase #6	$56.70	11.436%	$63.1842	$63.18	$63.20	$63.20
Purchase #7	$238.74	12.406%	$268.3581	$268.36	$268.35	$268.40
7 purchase totals =	$942.30		$1,040.6746	$1,040.67	$1,040.70	$1,040.70