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	$118.32	8.666%	$128.5736	$128.57	$128.55	$128.60
Purchase #2	$241.93	3.465%	$250.3129	$250.31	$250.30	$250.30
Purchase #3	$125.33	8.631%	$136.1472	$136.15	$136.15	$136.10
Purchase #4	$148.72	13.441%	$168.7095	$168.71	$168.70	$168.70
Purchase #5	$108.32	3.635%	$112.2574	$112.26	$112.25	$112.30
Purchase #6	$33.50	3.785%	$34.768	$34.77	$34.75	$34.80
Purchase #7	$163.25	4.763%	$171.0256	$171.03	$171.05	$171.00
7 purchase totals =	$939.37		$1,001.7942	$1,001.80	$1,001.75	$1,001.80