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	$148.94	4.643%	$155.8553	$155.86	$155.85	$155.90
Purchase #2	$239.90	3.451%	$248.1789	$248.18	$248.20	$248.20
Purchase #3	$63.93	12.815%	$72.1226	$72.12	$72.10	$72.10
Purchase #4	$229.59	10.861%	$254.5258	$254.53	$254.55	$254.50
Purchase #5	$208.90	8.193%	$226.0152	$226.02	$226.00	$226.00
Purchase #6	$164.46	4.425%	$171.7374	$171.74	$171.75	$171.70
Purchase #7	$162.56	5.674%	$171.7837	$171.78	$171.80	$171.80
7 purchase totals =	$1,218.28		$1,300.2189	$1,300.23	$1,300.25	$1,300.20