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	$84.55	11.261%	$94.0712	$94.07	$94.05	$94.10
Purchase #2	$185.95	4.279%	$193.9068	$193.91	$193.90	$193.90
Purchase #3	$205.93	10.484%	$227.5197	$227.52	$227.50	$227.50
Purchase #4	$25.43	8.326%	$27.5473	$27.55	$27.55	$27.50
Purchase #5	$188.55	8.417%	$204.4203	$204.42	$204.40	$204.40
Purchase #6	$148.30	4.853%	$155.497	$155.50	$155.50	$155.50
Purchase #7	$94.59	6.630%	$100.8613	$100.86	$100.85	$100.90
7 purchase totals =	$933.30		$1,003.8236	$1,003.83	$1,003.75	$1,003.80