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	$226.63	5.577%	$239.2692	$239.27	$239.25	$239.30
Purchase #2	$76.37	7.415%	$82.0328	$82.03	$82.05	$82.00
Purchase #3	$34.44	11.839%	$38.5174	$38.52	$38.50	$38.50
Purchase #4	$225.41	6.731%	$240.5823	$240.58	$240.60	$240.60
Purchase #5	$246.89	3.226%	$254.8547	$254.85	$254.85	$254.90
Purchase #6	$210.31	12.618%	$236.8469	$236.85	$236.85	$236.80
Purchase #7	$154.28	5.495%	$162.7577	$162.76	$162.75	$162.80
7 purchase totals =	$1,174.33		$1,254.8610	$1,254.86	$1,254.85	$1,254.90