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	$202.64	6.585%	$215.9838	$215.98	$216.00	$216.00
Purchase #2	$93.64	9.404%	$102.4459	$102.45	$102.45	$102.40
Purchase #3	$157.45	10.705%	$174.305	$174.31	$174.30	$174.30
Purchase #4	$201.96	9.184%	$220.508	$220.51	$220.50	$220.50
Purchase #5	$42.30	3.869%	$43.9366	$43.94	$43.95	$43.90
Purchase #6	$247.82	3.351%	$256.1244	$256.12	$256.10	$256.10
Purchase #7	$88.61	11.102%	$98.4475	$98.45	$98.45	$98.40
7 purchase totals =	$1,034.42		$1,111.7512	$1,111.76	$1,111.75	$1,111.60