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	$73.69	11.456%	$82.1319	$82.13	$82.15	$82.10
Purchase #2	$62.98	7.413%	$67.6487	$67.65	$67.65	$67.60
Purchase #3	$244.65	10.586%	$270.5486	$270.55	$270.55	$270.50
Purchase #4	$191.46	3.384%	$197.939	$197.94	$197.95	$197.90
Purchase #5	$104.45	4.709%	$109.3686	$109.37	$109.35	$109.40
Purchase #6	$183.89	4.292%	$191.7826	$191.78	$191.80	$191.80
Purchase #7	$215.75	7.280%	$231.4566	$231.46	$231.45	$231.50
7 purchase totals =	$1,076.87		$1,150.8760	$1,150.88	$1,150.90	$1,150.80