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	$43.85	5.190%	$46.1258	$46.13	$46.15	$46.10
Purchase #2	$98.25	5.627%	$103.7785	$103.78	$103.80	$103.80
Purchase #3	$230.72	11.448%	$257.1328	$257.13	$257.15	$257.10
Purchase #4	$202.92	12.633%	$228.5549	$228.55	$228.55	$228.60
Purchase #5	$158.64	11.163%	$176.349	$176.35	$176.35	$176.30
Purchase #6	$97.53	11.534%	$108.7791	$108.78	$108.80	$108.80
Purchase #7	$185.88	5.612%	$196.3116	$196.31	$196.30	$196.30
7 purchase totals =	$1,017.79		$1,117.0317	$1,117.03	$1,117.10	$1,117.00