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	$140.50	10.706%	$155.5419	$155.54	$155.55	$155.50
Purchase #2	$191.96	12.761%	$216.456	$216.46	$216.45	$216.50
Purchase #3	$187.34	5.156%	$196.9993	$197.00	$197.00	$197.00
Purchase #4	$68.37	4.808%	$71.6572	$71.66	$71.65	$71.70
Purchase #5	$50.43	10.312%	$55.6303	$55.63	$55.65	$55.60
Purchase #6	$244.34	6.377%	$259.9216	$259.92	$259.90	$259.90
Purchase #7	$219.78	9.205%	$240.0107	$240.01	$240.00	$240.00
7 purchase totals =	$1,102.72		$1,196.2170	$1,196.22	$1,196.20	$1,196.20