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	$118.93	4.228%	$123.9584	$123.96	$123.95	$124.00
Purchase #2	$92.53	4.241%	$96.4542	$96.45	$96.45	$96.50
Purchase #3	$182.89	11.786%	$204.4454	$204.45	$204.45	$204.40
Purchase #4	$217.44	3.413%	$224.8612	$224.86	$224.85	$224.90
Purchase #5	$33.47	11.635%	$37.3642	$37.36	$37.35	$37.40
Purchase #6	$45.47	3.735%	$47.1683	$47.17	$47.15	$47.20
Purchase #7	$244.64	8.703%	$265.931	$265.93	$265.95	$265.90
7 purchase totals =	$935.37		$1,000.1827	$1,000.18	$1,000.15	$1,000.30